Silly me, forgot to mention that the true name of Saigyou's daughter is forgotten. Because of this in order for her to have the dignity of a name now I can only think to call her "Yuyuko". Now I doubt that is her actual name, but it is the name she was given by ZUN. I guess it is better than not having a name so as someone who actually does care about her I do appreciate her once again having a name. So yeah, no wonder she would be eligible to end up in Gensokyo... even though again, Netherworld is not technically part of it. Odd thing, though, there is no reference to Yuyuko being a Buddhist nun even though not just her father became a monk, she became a nun, as did her mother. In the end, they entered paradise as a family one by one.
Shotoku, his bride, and another of his retainers on the other hand... well I guess they are only known to academics so maybe.
Hijiri, no idea but I know she and her brother existed some time ago.