Is the part in bold OK?

I think “King of Sutra” is not an appropriate name for a girl. Not only this but also according to the “Kyo’o Gozen gosho”, “Kyo’o is a dutiful child who will succeed in this lifetime.”(Gosho p.635) In ancient Japan, the custom was that only a man, and not a woman, could succeed and take over the headship of a family. So, I believe Kyo’o was a boy.

“King of Sutra” is not an appropriate name for a girl, if for no other reason than kings are men. Also, according to Kyo’o Gozen Gosho, “Kyo’o is a dutiful child who will succeed in this lifetime.”b(p.635) But in ancient Japan, supposedly only a man could succeed and take over as head of a family. So, Kyo’o must have been a boy.