Can you see Busan, Korea from Tsushima!? I went to check it out for myself: Thoughts on international exchange before the arrival of immigrants and Buddhism

The route and purpose of this trip

From June 8th to 11th, 2025, I traveled from Hakata to Tsushima and Busan.

The general itinerary was as follows:

Night of the 8th: Arrived in Hakata by plane from Hakodate via Haneda. Overnight stay only.
Morning of the 9th: Traveled from Hakata Port to Tsushima by high-speed jetfoil.
Afternoon of the 9th: Traveled across the island by rental car. Aimed for Kaneda Castle ruins, the Korea Observatory, etc.
Morning of the 10th: Went to meet the Taishu horse, a precious native Japanese horse that still remains on Tsushima.
Afternoon of the 10th: Crossed from Tsushima's Hitakatsu Port to Busan, Korea by ferry.
Morning of the 11th: Visited the Bokcheon-dong burial mounds and Beomeosa Temple in Busan, and returned home on an afternoon flight.

This itinerary mainly utilized ships. As you may have noticed, it was quite a whirlwind schedule.

Also, while a trip to Korea usually centers on gourmet food, beauty, and shopping, my purpose was, above all, research on immigrants (toraijin). Once again, this turned into a unique trip quite different from ordinary sightseeing.

That said, you might be wondering why I had to travel around Tsushima and Busan by ship for immigrant research. Or perhaps you are wondering why I am doing something as niche as immigrant research in the first place.

But for me, this holds extremely important significance when considering the history of Buddhism.

In the Buddhist industry, it is said that Buddhism was introduced to Japan in 538 or 552 from the country of Baekje in Korea. This also appears in Japanese history textbooks.

Learning the flow of Japanese Buddhist history from this point is the standard pattern for us monks, but honestly, I believe there is a blind spot in this kind of education.

That blind spot is the international situation before Buddhism was introduced to Japan.

"Why was Buddhism introduced to Japan?"
What did the existence of Buddhism mean in the East Asian situation at that time?

This is the key.

For us, who take the existence of Buddhism and temples for granted, we might not question the event of Buddhism's arrival, but in fact, the dynamism of the international situation at that time lies precisely here.

I value the idea that religion is not just religion. Religion is not established solely by doctrine, rituals, and faith, but is born from a complex intertwining of politics, economy, culture, history, international affairs, geography, climate, and ethnicity.

I cannot talk more about it here as it would take too long, but the reason I toured Tsushima and Busan on this trip was precisely because I had a great interest in this "international exchange before the arrival of Buddhism." And the perspective that gave me this was the book"Wa-koku Seen from Across the Sea" by archaeologist Kanta Takada.

I cannot forget the shock I felt when I first read this book.

It is well known that various technologies were transmitted from Korea to ancient Japan, but I was surprised that the 5th century was even called the "century of technological innovation."

And if you read this book, you will also learn that such exchanges with Korea continued intermittently from the latter half of the Yayoi period, let alone the 5th century. I was also surprised to learn that by the 3rd century, there was already quite close cooperation between coastal villages. This was unexpected, considering the history of the Kentoshi (missions to Sui) around 600 AD and the subsequent frequent shipwrecks of the Kentoshi (missions to Tang). Korea, Tsushima, and northern Kyushu were far more international than we had imagined.

That is precisely why I decided to travel by boat from Hakata to Tsushima and then on to Busan. It is the stage for international exchange that has been active for nearly 2,000 years. I really wanted to feel the sense of distance between Tsushima, the gateway to Korea and Japan, and Hakata. That is what I thought when I planned this trip.

And another thing I would like to share is the astonishing level of technology brought to Japan by the Toraijin (immigrants from the continent) through these international exchanges.

These are earrings from around the 5th century unearthed from the Bokcheon-dong burial mounds in Busan, but just look at them! I was blown away by this sophisticated design. I first learned about these kinds of accessories from a book called 'Archaeology of Accessories' by Professor Kanta Takada. It was the Korea of that time that possessed such ultra-advanced technology, and the Toraijin who came over from there brought various technologies to Japan. Of course, Buddhism is one of them.

Well, the introduction has become quite long, so I would like to finally get into the details of the trip. In this article, I will introduce my landing on Tsushima, the Kaneda Castle ruins, and the Korea Observatory where you can look out over Busan, South Korea.

From Hakata to Tsushima by Jetfoil high-speed boat

On June 9, 2025, I took a bus from Hakata Station to Hakata Port.

Since the rainy season had already begun in Kyushu, the weather was unfortunately rainy. Fortunately, there was almost no wind, so I probably didn't have to worry about the boat rocking.

This is the high-speed Jetfoil boat.

Operated by Kyushu Yusen, this boat departs Hakata Port at 10:30 AM, stops at Iki, and arrives at Tsushima's Izuhara Port at 12:45 PM.

Looking at this map, you can clearly see how close Tsushima is to Kyushu.

And if you look at an even larger map, you can see that Tsushima is located exactly in the middle of Kyushu and South Korea. By the way, it is about 50 kilometers from the northwestern part of Tsushima to Busan, and they say you can see each other on clear days. It is said that exchanges have been going on since ancient times under such a sense of distance. Having a foreign country at such a close distance is a difficult feeling for me to grasp, as I am from Hakodate, Hokkaido, but it might be similar to the feeling of looking across at Oma, Aomori Prefecture, from Hakodate. Of course, Aomori is not a foreign country, but if I think that the land visible on the other side is a foreign country, to be honest, it feels quite scary, or rather, it makes me brace myself.

In any case, grasping this sense of distance on-site is the purpose of this trip. That is why I chose this route by boat instead of by plane.

Now, we are setting sail.

As expected of a high-speed boat, I can feel the considerable speed. It is said that it can reach speeds of over 70 kilometers per hour.

We are crossing the Genkai Sea.

In less than 30 minutes, the island of Iki came into view. It really is close...!

Around 11:30 AM. We arrived at Iki in no time. Even though it is a high-speed boat, I can't believe it took less than an hour.

And soon we will be departing Iki as well. From here, it will take about another hour to reach our destination, Tsushima's Izuhara Port.

As expected, I couldn't see the silhouette of Tsushima island immediately after departure, but after about 30 minutes, the shape of the island began to emerge faintly in the direction the boat was heading.

If it had been a clear day, I might have been able to see it sooner.

I am finally getting close to the island. I will be arriving soon.

Even so, the mountains start right from the shore, and everywhere I looked, it was mountains, mountains, mountains. I was surprised by this. But that is to be expected, as nearly 90% of Tsushima's land is said to be mountainous. I would constantly realize this even after landing and while traveling by rental car.

Now, I have arrived at Izuhara Port.

The understated sign that reads "Japan Heritage: Border Island" has a certain charm to it. I rented a car at a rental shop right near this port and started my journey by car from here.

According to the staff at the rental car company, nearly 90% of the people who rent cars here are South Korean, and it is rare for a Japanese person like me to come. At that point, I was half-skeptical that so many Koreans were coming here, but I would soon come to understand the meaning of those words very well.

Visiting the Kaneda Castle ruins to see the defensive walls built in the 7th century—What were the aftereffects of the Battle of Baekgang where Japan was soundly defeated by Silla?

My first destination on Tsushima is the Kaneda Castle ruins, located in the center of the island.

It is a distance of a little under 40 minutes by car from Izuhara Port to the Kaneda Castle ruins trailhead.

Since it is called the Kaneda Castle trailhead, Kaneda Castle is a castle built in the mountains. Let's look at the explanation on the sign.

As written here, this Kaneda Castle was built by the Japanese side after they were defeated in the Battle of Baekgang in 663, out of fear of subsequent invasions by Silla and Tang.

I learned about the Battle of Baekgang itself in my Japanese history textbooks, but here, my past memories and real-life experiences were finally connecting.

And the reason I became interested in these Kaneda Castle ruins in the first place is, as expected, because of a certain book I read. That book was "Asuka no Miyako" (The Capital of Asuka) by Shinji Yoshikawa.「飛鳥の都」 was the book.

According to this book, after the Battle of Baekgang, there was a very real sense of crisis that Tang and Silla would attack Japan. And it was a very interesting development that this sense of crisis—that "Japan will perish as it is"—led to centralization, in other words, the strengthening of the Ritsuryo system. At the same time, the fact that the trend of state-protecting Buddhism also accelerated is a point of great interest to us monks.

From this perspective, the defensive wall ruins of Kaneda Castle are a truly grateful spot for me to feel the sense of crisis in Japan at that time and the sense of distance from Korea. That is exactly why I have come all this way.

The road to the trailhead is truly in the mountains. I pass through unpaved roads.

Now, I have arrived at the entrance to the trail. There was a sign here too, so let's take a look.

According to this sign, it is about a 50-minute walk from the trailhead to the summit, and about a 30-minute walk to the Sannokido gate where the stone walls are located.

For now, I decided to start walking toward the stone walls, which were my destination.

Tsushima is, after all, a southern island. I think the rainy season has started, so it feels quite humid. Also, the plants growing here are jungle-like. Insects of all sizes are flying around, buzzing. Honestly, it's quite eerie.

And I really want you to see this video.

As I was walking along the path, I heard a rustling sound. I turned around, thinking an animal might have come out, but there was nothing there. I kept walking for a while, feeling uneasy and wondering what the sound was, but then I realized what it was.

It was a crab, of all things.

The left side of the path was a rocky cliff, and it was damp, so it seems like crabs have made their home there. The crab in this photo is small, but I encountered larger ones many times after this. There were also crabs with dazzling yellow colors and flashy patterns, which made me feel that this is indeed a tropical country.

Even so, there were so many of these crabs that the rustling sound made me shudder every time... This is tough. It doesn't feel like a fun hike at all.

And if I turned my eyes to the other side, there was a dense, damp, jungle-like thicket of plants. I can't walk here with a light heart anymore. It's scary. I underestimated this mountain...

I climbed Mount Hiei just one week before this trip to Tsushima and Busan. I talked about the record of that time in the article “Mount Hiei Hiking Journal (Kyoto Shugakuin to Enryaku-ji) - Reliving the Kirara-zaka route that Shinran Shonin also walked!””, and I was able to walk through the hike on Mount Hiei very happily without feeling much danger to my life.

It is true that there are some steep sections on the mountain trails of Mount Hiei, but unlike this mountain of Kaneda Castle, there was little humidity and no jungle-like atmosphere at all. It felt more like a dry, rocky mountain, and I felt almost no threat from dense plants or insects.

For a weakling like me who is used to city life, the presence of a damp jungle and insects is more terrifying than anything else... This hike up Kaneda Castle in Tsushima is the very definition of humidity and jungle, which I am not good at. This is tough...! I decided to climb quickly to finish it as soon as possible.

This also looks bright in the photo, but it felt extremely dark on-site.

Please, give me a break. It's scary. Insects are buzzing around me. And they are so persistent! They keep following me. Maybe several of them were following me in a relay, but I'm about to cry.

Even so, the Japanese military was stationed on such a southern island during the war. This Kaneda Castle also has a past as a military garrison. The soldiers who fought in the Southeast Asian and Pacific theaters served in even harsher environments than this... I couldn't help but shudder at that thought.

I passed through the dark jungle path, and soon a bright view came into sight. It's the sea.

Tsushima is also famous for the beauty of such intricate inlets. It must have been the perfect land as a base for a maritime village precisely because it has such inlets.

As I went further, something that looked like a stone wall appeared in front of me.

There was a sign, so there is no mistake. I have arrived at my destination. It took about 30 minutes from the trailhead.

If you go past the sign, you can clearly see that the stone wall was built on a steep slope facing the sea.

As explained on this sign, this stone wall and the building ruins were built in the latter half of the 7th century, that is, after the Battle of Baekgang.

The stone wall is built along the mountainside.

There seems to be a spot called the Southeast Corner Stone Wall Observation Point, so I decided to head toward it.

As you can see if you watch the video, it is thrilling because you are walking almost entirely along a cliff.

The stone walls are uniformly about 4 meters high, and this section is said to preserve the state of that time relatively well.

They say that South Korea can be seen from Tsushima with the naked eye. This castle was built in preparation for the terrifying situation where a large army might surge from such a country. The fact that many Japanese soldiers were sent to the Battle of Baekgang shows that transporting large troops to the Korean Peninsula by ship was being done without issue even back then. And the same is true for the reverse. If a powerful Silla or Tang army were to attack in earnest, it was inevitable that they would first target Tsushima, which is closest to South Korea. And if this place fell, an attack on Kyushu would be easy. This place is truly the front line of national defense. I felt that tension myself at these stone walls.

And the Emperor at the time was Emperor Tenji. He is the very same Prince Naka no Oe who carried out the Taika Reform. This stone wall is connected to a big name that you always see in history textbooks. I was excited by the romance of that history.

Now, time to return. I came down along the cliff, so I am drenched in sweat on the way back.

Before coming here, I had planned to go to the top of the Kaneda Castle trail, but I gave up here. I am retreating.

They say it takes about another 30 minutes to get to the top from here, but to get to the top, I would have to walk that jungle path again. Time-wise, the time limit was approaching. This is a courageous retreat.

Besides, my spirit was already completely broken.

As I mentioned earlier, I was completely defeated by this jungle-like environment. Furthermore, I didn't notice it on the way there, but there were hornets and giant horsefly-like insects buzzing around the path near the stone walls.

Come to think of it, there was a sign like this at the entrance to the mountain trail...

This is it! There really were hornets!

Moreover, I hadn't thought this hike would be such a full-scale mountain climb, so I had come in a black windbreaker and black pants. This is the worst. With hornets swarming in a place like this, I wouldn't have enough lives to spare.

I ran almost the entire way back down. The rustling sound of crabs also continued to startle me.

I was naive...! This was not a place to come to lightly...! With the single-minded desire to escape as quickly as possible, I returned to my car.

To the Hill Where You Can See a Foreign Country Observation Deck

Although I was completely defeated by the jungle-like mountain path of Kaneda Castle, I pulled myself together and set off for my next destination.

I am now heading to the "Hill Where You Can See a Foreign Country Observation Deck," located on the coast in the northwestern part of Tsushima.

It is about an hour and 20 minutes by car from the Kaneda Castle ruins. I felt it keenly during this trip, but Tsushima has so many mountains! I rarely hit any traffic lights and was driving through the mountains almost the entire time, so it was almost non-stop.

Now, I have arrived at the Hill Where You Can See a Foreign Country Observation Deck.

However, unfortunately, there was a haze on the Korean side, so I couldn't see Busan.

I also went up to the second floor of the observation deck.

It seems that when the weather is nice, you can see Korea quite clearly.

Although I couldn't see it this time, I did what I set out to do. I have no regrets. Korea is on the other side of that haze. Just being able to feel that was a stimulating enough experience for me.

And when I was about to leave this observation deck, this message was sent to my smartphone.

To my surprise, it seems this place was within the range of Korean radio waves! This was an experience that made me feel the closeness to Korea from this perspective as well.

To today's final destination, the 'Korea Observatory'

About 30 minutes away from this hill observatory where you can see a foreign country, there is another famous spot where you can look out toward Korea.

That is this Korea Observatory.

I arrived just after 5:30 PM, so I couldn't enter the building, but I was able to look out toward Korea from outside the building without any issues.

Unfortunately, I couldn't see Korea here either, but it was truly pleasant to just stare at the sea while feeling the ocean breeze. By the way, the small island in front is apparently an Air Self-Defense Force base.

After finishing at the Korea Observatory, I headed to my accommodation near Hitakatsu Port in northern Tsushima.

I stayed at the Toyoko Inn Hitakatsu. I decided to stay here because of its location near Hitakatsu Port and the reliability of the Toyoko Inn brand.

I finished checking in, left my luggage in my room, and set off for dinner.

After looking it up online, I decided to visit this restaurant, Mimatsu, which had reviews calling it Tsushima's soul food.

It was nighttime, but I had this lunch set. A simple, nostalgic taste...! It was very delicious. I was very satisfied.

There is no parking around the Mimatsu restaurant, and you have to go park your car across the river? in front of it, but that path left a strong impression on me.

There is a parking lot for Mimatsu on the right side of the photo, and the way the cars were parked along this river reminded me of Delft in the Netherlands.

Delft, the hometown of Vermeer, is a city with very deep memories for me as well. I talk about that experience in my article “Strolling through the places associated with Vermeer in Delft, Netherlands!”, but I felt that same atmosphere in the river near Mimatsu as well.

Well, after recharging my energy with a delicious dinner, I headed back to the Korea Observatory.

Since it is June, the days are long. It is this bright at 7:30 PM.

It is nice. It has a great atmosphere.

However, it is a shame, as I still could not see South Korea...

But my main goal was the night view of South Korea that is said to be visible at night. If it is the lights of the night view, perhaps I might be able to see it even in this weather. I decided to bet on that last hope and stick it out until the very end.

It has finally started to get dark.

I briefly hoped that the light visible over there was South Korea, but it seems to be a ship. I also suspect the strong light on the right is probably not from South Korea.

Hmm, this looks like it is not going to happen... Although there are lights visible over there, it does not seem to be the city of Busan. The haze must be quite thick after all.

I stuck it out until around 8:30 PM, but the situation did not improve. It is frustrating, but I am retreating.

It is completely night all around.

I headed back through the pitch-black mountains and returned to the hotel for the day. That was the end of a hard day.

The next morning, I came back to the observatory for a rematch, but the haze had become even thicker, haha.

It is completely hopeless now, haha.

I have no choice but to laugh.

However, the observatory was open at this time, so I decided to go inside.

Inside, there were explanatory materials and videos playing, introducing the scenery that can be seen from this observatory.

I was surprised to see that you can see the city of Busan so clearly when it is sunny.

From Hakodate, where I live, I can see Oma on the Shimokita Peninsula in Aomori Prefecture.

Oma is famous for tuna, and the distance between Oma and Hakodate is about 18 kilometers. Tsushima and Busan are about 50 kilometers apart, which is more than double the distance, but I could not help but think that the feeling of seeing the opposite shore must be the same.

Although the haze made it impossible to see the other side at all, it was a grateful harvest to be able to see these materials.

After this, I went to meet the Taishu horse, a precious native Japanese breed, and the weather started to get incredibly nice!

I will talk more about these Taishu horses in the next article, but after meeting them, I headed back to the Korea Observatory.

This makes it my fourth visit to the observatory in total. With dusk, night, morning, and now daytime, I have covered almost every time of day. Maybe I can see it this time!

At this time of day, there were also tour groups from South Korea. I will talk more about this in a later article, but Tsushima seems to be extremely popular with tourists from South Korea.

Oh! How about this!

Could that possibly be land visible over there!

This is so exciting!

An eagle appeared flying in the sky, too. This really gets my spirits up. I finally saw Korea!

Well, I finally saw it on my fourth try. I was staring intently, thinking about how close Korea really is, when I suddenly realized something.

The black line that looked like land was moving...

That's right, the line that looked like an island was just clouds. I was so disappointed. This is exactly what you call a false joy. In the end, I couldn't see Korea after all. I can only laugh.

That said, it seems that Korea is generally hard to see during this summer season. When I asked a driver in Busan the next day, he told me that the best time to see each other clearly is in winter when the air is crisp. A clear winter day seems to be the best timing. That means coming here with such enthusiasm during this season was quite a challenge in itself.

Well, in any case, Korea lies beyond the view from this observatory. Having a foreign country within visible distance is unique to Tsushima. It is a feeling that is hard to grasp when living in Japan, but this visit made it very clear that Tsushima is a gateway for international exchange and the front line of national defense.

In the next article, I will talk about the precious native Japanese Taishu horse that I introduced briefly earlier. I hadn't originally planned to go into such depth on this note, but the experience I had here was so wonderful that I would like to share it with you. I am sure you will be surprised when you read the next article. I hope you will continue to follow along.

To be continued

Next article here

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