The Story of Creating a Vertical-Writing EPUB and Publishing on Kindle
~Introduction~
This is not a proper how-to guide.
(Which is why it is free.)
It is merely a record of my personal attempt.
Please use this as a reference for your own research and progress, including how I got started.
I hope that even an article like this can help someone with their self-publishing.
It is mostly a memo for myself.
1. Writing the Manuscript
Google Docs is best.
Google Docs is where you should do your writing.
Please copy and paste any works you have already published on note.
Even for works on note that only have a title and body text, it is better to include an
afterword.
If possible, a prologue as well.
It seems best to follow the same style as books sold in bookstores.
Let's complete the additions and corrections to the main text at this stage as well.
If you start making corrections later, you will pursue them infinitely,
so I would like to finalize it here as much as possible.
In my case, I was particular about vertical-writing publication, so in this article, I will proceed with the steps to convert it into an e-book using
Densho-chan's Denden Converter. If you are doing how-to guides or if a horizontal-writing style is more suitable, Amazon's
Kindle Create is recommended, so please check that out.
Densho-chan's Denden Converter can of course also be used to create it, so it might be good to try creating it once using the steps in this article.
2. Adjusting Line Spacing, etc. with Markdown
I think it is the same for others, but when you convert to an e-book using
Densho-chan's Denden Converter, the line spacing in particular tends to be compressed.
Therefore, I will process it in advance so that the line spacing is correct.
If you enter <p><br /></p> on a line you want to be blank, that line will become blank when it becomes an EPUB file, leaving one line of space.
If you want to leave two lines of space, you can just enter <p><br /></p> on the two lines you want to leave blank.
For other things like pasting images such as illustrations or ruby, you can also control the display using symbol notation in the same way.
This method is called Markdown, and Denden implements its own unique Markdown.
For details, please check Denden Markdown.
Let's complete all adjustments and image insertions using Markdown at this stage.
Although, I will probably end up repeating the adjustments after this.
3. Exporting the Text File
Google Docs file -> download, and export with the
.txt file extension.
I think I will repeat this many times after this, so let's save it with an easy-to-understand name with numbering, like a date.
If you have illustrations, etc., it is easier to handle later if you collect them in a folder with the
.jpg extension together with the text file.
4. Converting the Text File to EPUB
Here is finally the turn for Densho-chan's Denden Converter!
1. Enter the work title and author name in the "Enter information!" section.
2. For vertical writing, select "Right to Left (Vertical Writing)" in the page turning direction field.
3. You don't necessarily need to touch the "Right-hand preferences" section. Adjust as needed.
4. Press the browse button in the "Upload!" section, select the text file and all images except for the cover to be included in the book, select multiple files using the Ctrl key, etc. and upload them. *The cover is registered on Amazon KDP.
5. Check the created EPUB preview and let's convert it.
With this, the automatically created EPUB will be saved.
A preview will launch, so check it roughly.
With this Denden preview, the display might look strange in some cases.
Since the line spacing and page intervals are mainly what look strange, don't worry about it here.
What you should check is whether all the files you threw in are present.
If an image is missing, please check.
Usually, it's because the image extension itself is different, for example, it's a .png, or the markdown notation is incorrect.
If it's only a text file, it should be mostly okay.
Let's give the finished EPUB a name, such as the work title.
5. Checking the finished EPUB
Read and check the finished EPUB using the actual Kindle app.
Send to Kindle and log in with your Kindle account.
If you don't have a Kindle account = Amazon account, let's create one.
Once you are logged in, upload the EPUB from earlier into the gray box labeled Send files to Kindle library.
After a short while, you will be able to download and read the uploaded EPUB on the Kindle app of the same account.
At this point, Neko was moved!
The reading material I created can be read on an e-book platform that everyone knows!
You get all excited!
It's a good time to take a short break.
After this, the hell begins.
If you can prepare two devices, please do so.
I think a PC + smartphone or tablet is best. PC + PC is also fine.
On the PC, keep the initial Google Docs open.
This opens the final updated file converted to text.
On your smartphone or tablet, open the Kindle app and open the downloaded EPUB.
Even if you are doing it with one smartphone, do the same by opening Google Docs and Kindle, and keep them ready to switch immediately.
What you need to do is simple.
Read your work on Kindle, and if there is a problem, correct the manuscript in Google Docs each time.
The check items are,
・Typos and omissions
・Punctuation
・Paragraphs, line spacing
・Dashes, ellipses
・Whether markdown functions are working
・Reading experience with vertical conversion
Is it around here?
In addition, regarding changes in expression and new additions, I recommend once again that you solidify these as much as possible at the initial stage.
This is because this is the stage to devote resources to improving the reading experience.
Parts that read with good rhythm in horizontal writing might feel a bit awkward when changed to vertical writing.
Find such places and adjust line breaks, line spacing, or punctuation.
Focusing on dialogue and sentences with important meanings, be sure to carefully examine the punctuation.
Also check for typos and omissions that should not exist, and notation errors such as dashes and ellipses.
Especially with dashes and ellipses, the appearance is hard to distinguish, and you might notice for the first time in vertical notation that you were using different bars or dots.
Also, don't forget whether Denden's markdown is functioning.
Are the images placed in the correct position?
Are ruby and emphasized text okay?
Let's check page by page to see if it is the page you envisioned.
Once all checks are complete and you think, "Okay, I can submit to KDP!", return to the page for
3. Exporting the text file and repeat the same thing again.
Save the newly created EPUB with a different name (numbering, etc.) so you can identify it, and check it strictly from the same perspective as before.
I recommend repeating the same process at least three times to polish it.
Neko, partly because it was the first time and I was inefficient,
repeated it more than 10 times.
6. Just throw it at Claude!
I think it's fine for the purpose of tidying things up to a certain extent beforehand. I export from
Google Docs as a PDF and have Claude read it. You can have it do a rough pass by asking it to list issues like typos, omissions, punctuation, and grammar. However, when I actually checked it manually afterward, errors kept popping up. It seems that the more characters a work has, the more likely it is that oversights will occur. This is because the token count is limited. In another work, it skipped an entire section, so there were times when it couldn't understand the intent of my questions. And there is no doubt that the closer you get to literary works, the more there are limits to interpretation. Although, compared to a certain Mr. ChatGPT, it seems to be quite a bit more flexible.
If it's just for pure proofreading, I think you can rely on it quite a bit if you break it up into chunks of at most one chapter at a time.
7. Registering for Self-Publishing KDP
It's fine to do this first as well. Neko registered right at the very beginning just in case.
KDP stands for Kindle Direct Publishing. It's like, "Everyone can publish directly to Kindle."
What you need for registration is:
・Amazon account (create a new one if you want to separate it from your regular shopping) ・Bank account ・My Number Card ・Your address in English (if you are not used to writing in English, do it in advance)
Actually, I don't remember the details very well anymore, so I'll just cover the sticking points.
The problem where the address must contain two alphabetical characters
The KDP address registration itself is fine in standard Japanese format, but when registering a bank account, entering the address normally results in an error. It seems that the system requires at least two alphabetical characters no matter what, and when I consulted ChatGPT, it told me to add a meaningless 'ab'. After registration, there was a 1-yen transfer test, and since it was deposited successfully, it seems this way is fine.
101 Shiranami-ro, X-X-X, X-City, Tokyo
→ Wouldn't go through without alphabetical characters...
101 Shiranami-ro, X-X-X, X-City, Tokyo ab
→ Went through successfully with two mysterious alphabetical characters. Isn't that strange?
The problem where you can never finish saving because of Brazil
This is also a money-related issue. I was able to register my bank account successfully with the 'ab' mentioned above, but for some reason, I was confused because I couldn't proceed to save.
Even when I asked ChatGPT, it just kept repeating things it didn't actually know, leading me astray significantly.
If I proceeded to US tax registration, the bank account registration would be reset, and it would tell me to register a bank account. When I entered the bank account registration again, there were blank fields, and I couldn't save.
The cause was an error message stating that if a customer in Brazil bought the book, cash transactions could not be processed.
Neko interpreted it as 'Oh, I can't sell books to people in Brazil,' but this was an error message saying that because cash transactions aren't possible, you need to set up checks. So, I set up checks so that customers in Brazil could also buy it, and that was it. I was able to save successfully and proceed to the next US tax registration. These were about the only two points where I got stuck, and you can register if you do it while asking an AI or something.
After that, just follow the instructions to
upload the EPUB you created and the cover art. I apologize for being so vague about this part.
Be sure to check things like cover art size with ChatGPT or similar tools.
Regarding revenue, it differs slightly between KDP Select, which is an exclusive Kindle distribution agreement, and standard distribution.
With KDP Select, you get 90 days of exclusive distribution—meaning you cannot post the work on platforms like note or sell it in other stores—but in exchange, your work is included in Kindle Unlimited (the all-you-can-read plan), allowing you to earn revenue based on the number of pages read in addition to standard sales revenue.
It looks attractive, but if you are trying to do both paid note and Kindle,
or if you have already posted the original work on note, you would need to take it down, which makes it a difficult decision.
It might be a good idea to think about how you want to handle this in advance.
Once all settings and uploads are complete, the book will go on sale after a review period of up to 72 hours.
—In Conclusion—
I usually only write works that lean toward literature,
(Can those even be called literature?)
so I am really not good at these kinds of how-to guides.
I imagine there were parts that were hard to read or confusing.
To those who read until the end, thank you so much.
I hope that even an article like this
can help lead someone to say, "I was able to publish!"
Thank you very much.
April 2026
Neko🐈
