Hatsui (室宿?) is a Genbu Celestial Warrior and the son of healers. His true name is Zara Erutai (ザラ-·エルタイ, Erutai Zaraa?), born under the star Encampment (室), . He possesses the ability to shoot spikes from his body and the ability to form a steel cage/basket around himself and others as a means of protection. He is timid, shy, and cries easily and finds it difficult to trust others.
When he was nine, Hatsui's parents died and left behind large debts to pay off. When villagers began to pick on him, he accidentally unleashed his celestial power for the first time and ended up killing many people. Though he had acted in self-defence and he did not have any intention of hurting others, Hatsui ran away from his village and secluded himself. Sometime later, a woman named Fen discovered him there and befriended him. However, when Takiko and Tomite arrive to find Hatsui, it is revealed that Fen is an assassin with a mission to kill the Genbu Celestial Warriors and their priestess. After rescuing him from Fen, Hatsui becomes the third Celestial Warrior to join Takiko.