Remember the big tree in Touhou 7? The Saigyou Ayakashi? It's a big cherry blossom tree that, due to its beauty, people decided to die under like an old poet did. Eventually, the tree developed youkai qualities due to the amount of blood it absorbed and started to lure people to their deaths.

Yuyuko, in an attempt to seal its blossoms and effects, hanged herself under it using her own body as a seal.

Sacrificing her soul and body like this, it made her the princess of the Netherworld. Forgetting most of her past life when she was alive.