Long ago, a talented poet traveled in Gensokyo who became aware that his death was near, choosing to find his final resting place under the tree. After the poet's death, the word of the cherry tree's beauty began to spread across the land, and the tree had grown more beautiful since then, charming many near-death mortals into resting in peace beneath its blossoms. The tree became known as the Saigyou Ayakashi, developing the powers of a Youkai after a while. As a Youkai, the tree's beauty and charm increased even further, driving everyone who approached it to insanity with deadly peacefulness. The Ayakashi had drained too many human souls and became a danger to everyone, leading some unknown heroes to seal away its blossoms using Yuyuko's soul as the main component. The seal would freeze both the blossoms and the soul in place together for eternity.
In Perfect Cherry Blossom, Yuyuko's ghost tried to overpower the seal on the Saigyou Ayakashi in order to see the blossoms again and revive the soul from within. However, she was unaware that the sealed soul was in fact her own, and thus all of her attempts failed due to her unconscious self-preservation.
The Saigyou Ayakashi is simply a large cherry blossom tree with cherry blossoms that never fully bloom.
- Yuyuko Saigyouji (Sealed soul)
- Youmu Konpaku (Gardener)
- The poet referred to in the Saigyou Ayakashi's story is most likely Saigyou, who was a famous ancient Buddhist poet with a love of flowers, a passion for singing about it, and a desire to die beneath flowers.
- Ayakashi are supernatural beings, very similar to Youkai. The tree's name would therefore mean something like "Youkai of Saigyou".