Stories of the Japanese People 00990 [Early Northern and Southern Courts Period] The 3rd Northern Court Emperor, Emperor Suko
The blood relations are so complex that I may not be explaining them well. I really must use a diagram to explain this.
October 27, 1348 (Shōhei 3 / Jōwa 4). Emperor Kōmyō abdicated, and the Crown Prince, Imperial Prince Okihito, ascended to the throne. He became the third emperor of the Northern Court, Emperor Suko.
As mentioned earlier, the Retired Emperor Kōgon had previously instructed the Crown Prince, Imperial Prince Okihito:
"You may ascend to the throne, but after you, you must ensure that the imperial throne is passed to (my secret child) Imperial Prince Naohito."
(Refer to episode 00969).
With the accession of Emperor Suko, the question of who to appoint as Crown Prince arose. Naturally, the Retired Emperor Kōgon, the central figure of the Northern Court, intended to appoint Imperial Prince Naohito as Crown Prince, but there was another person who put themselves forward: Imperial Prince Kuninaga (1302–1375) of the Daikakuji line.
Wait, why was an imperial prince of the Daikakuji line in Kyoto instead of Anō, competing with the Jimyōin line for the position of Crown Prince? This has a very complicated history.
In the first place, Emperor Go-Daigo was the younger brother of Emperor Go-Nijō, and their father, the Retired Emperor Go-Uda, had decreed that "in the future, the Go-Nijō line should inherit the imperial throne," positioning Go-Daigo merely as a stopgap.
However, because Go-Daigo thought to permanently seize the imperial throne from his brother's line, the Daikakuji line split into two: the Go-Nijō line and the Go-Daigo line. And so, Imperial Prince Kuninaga, who was the son of Go-Nijō, remained in Kyoto without joining Go-Daigo, despite being of the Daikakuji line.
Imperial Prince Kuninaga desperately lobbied, saying,
"I want you to appoint me as Crown Prince so that the Jimyōin line and the Daikakuji line will continue to alternate on the throne in the future,"
but Tadayoshi rejected this and had Imperial Prince Naohito appointed as Crown Prince. Tadayoshi likely wanted to avoid further splitting the imperial line and causing more chaos.
Incidentally, there is a noteworthy fact about Emperor Suko. He is the common patrilineal ancestor of the current Imperial Family and the former imperial families.
In 1947, the Japanese government, under the occupation of GHQ, was instructed to drastically reduce the number of imperial family members, and 51 members from 11 branches were removed from the imperial register. These 51 people are called the "former imperial families."
When looking only at the patrilineal line, the blood relationship between these former imperial families and the Emperor is surprisingly distant, with Imperial Prince Fushimi no Miya Sadafusa (1372–1456) being the common ancestor. In other words, if you trace the patrilineal ancestors of the current Emperor and also trace the patrilineal ancestors of the 51 former imperial family members, the first person they have in common is Imperial Prince Sadafusa.
The grandfather of Imperial Prince Sadafusa was Emperor Suko. Therefore,
"If by any chance no male in the patrilineal line is born into the current Imperial Family, we should restore the males of the former imperial families to the imperial family,"
is a topic of discussion, but in that case, the person who would newly ascend to the throne would be doing so on the basis of being "a patrilineal descendant of Emperor Suko," and there are some who argue that this is, after all, too distant.