Saisei is a zombie who fights for Saishi. She uses a naginata to fight with.

In the manga, Saisei was killed by Akira after he defeated her ability to warp damage to her opponent, but he respected her since she was fighting so hard to protect Shinrei, whom she secretly loved.

In the anime, she fought with Benitora and Migeira at the Mibu Castle gates. She "devoured" Yuya by absorbing her into her endless space body, but was defeated by Yuya from within.