The plan Vexthra came up with hinges on whether Unity can possess Risana's body. If she were to suddenly appear inside the cage, it would cause fear and panic, which would then draw the attention of the Immortals.
That would take away her chance to activate the talisman.
So she had to possess her body, and since she was once Vexthra's sister, she had the best way to put her to sleep.
They grew up in a garden city where cherry blossom trees are everywhere.
Vexthra hated them, but her sister loved them. She even came up with the perfect cherry blossom tree and the settings it should be in to qualify her aesthetic.
Every night, before they went to bed, she would imagine that tree, and after doing it for years, it became her bedtime story.
Vexthra knew deep within her that Risana was indeed her sister, so she made the call, and Unity went ahead with it.
