Perhaps it was because of her carefree afterlife, or maybe the record had aged beyond recognition, but Yuyuko ultimately failed to realize that the girl who was written about in the record... was herself.
In the beginning, Yuyuko only possessed the ability to the extent of manipulating departed souls. Unconsciously, that power grew stronger, that eventually she possessed the ability to the extent of manipulating death. Terrified by her own ability, she committed suicide.
After becoming a ghost, she thoroughly forgot everything about the time she was alive, and started to enjoy being able to invoke death.
The reason Yuyuko can neither reincarnate nor vanish is because of the seal on the Saigyou Ayakashi. Once the boundary is breached, the time that was frozen will continue to flow, resulting in her death again. Reviving the corpse will destroy Yuyuko's ghost, so it's no wonder that the near-success of the revival ended in inevitable failure.
After all, Yuyuko is not able to manipulate anything but death.
The only person who knew the whole story, Youki Konpaku, grew slowly older due to the nature of half-humans, and disappeared with the belief that Youmu could inherit the truth about Yuyuko.
For all time, Yuyuko will remain as the princess of Netherworld and mistress of long-dead Saigyouji clan.
- She shall never bear witness to the blooming of the Saigyou Ayakashi.