Yuukei, the central protagonist, is an astronaut from Earth exiled to a remote penal colony planet after attempting to overthrow the dictatorial ruler Phippo within Earth's planetary federation. This political dissent defines his banishment. During isolation, he sustains a connection to Earth through memories of his girlfriend Anny, reinforcing his burdens of separation and unresolved relationships.

Upon arrival, Yuukei confronts an elderly woman locally feared as a murderous witch. His government mission requires investigating alleged foul play and eliminating her, establishing his role as an assassin. The planet’s barren, asteroid-like environment amplifies their confrontation's tension.

Their prolonged interaction drives the narrative. The witch reveals unexpected truths about life and love, challenging Yuukei’s preconceptions and mission objectives. A critical flashback introduces new characters and pivotal information, transforming Yuukei’s understanding of the witch and her circumstances, shifting his mission from elimination to comprehension.

The story adapts the Japanese Noh drama *Kurozuka*, paralleling Yuukei with the Noh character Yūkei/Tōkōbō—a monk encountering the onibaba of Adachigahara legend. This connection emphasizes themes of hidden humanity beneath monstrous exteriors and the pursuit of truth.

Yuukei’s development culminates in reassessing his mission. Revelations about the witch’s history compel him to transcend his government mandate, leading to a climactic realization about her identity and his purpose. His journey evolves from political enforcer to a seeker grappling with morality, truth, and shared humanity.