Muneto Ungyōsai, a timid college student and heir to a Buddhist temple, balances his familial legacy with clandestine duties as a junior agent of the Interplanetary Mutual Observation Agency. His father, the temple master, attributes extraterrestrial incursions—manifested as destructive "demon beasts"—to ancestral karma, anchoring Muneto’s battles in spiritual reckoning. The conflict intensifies when Kayō Asakura, his high school love, is marked by alien forces for hybridization, intertwining personal vulnerability with cosmic warfare.

Amid escalating threats, Muneto allies with his uncle Munechika, a yamabushi mystic, to combat the Hybrid—a human-alien entity central to the invasion. After the demise of veteran operative Shin’ichi Kasu, Muneto steps into broader agency responsibilities, partnering with driven colleague Jun’ichi Yagami to counter extraterrestrial task forces and cults reviving the Hybrid across dimensions.

His journey traces a reluctant evolution from apprehension to strategic engagement, driven by temple-born duty and loyalty to the agency. The struggle spans reconnaissance, interdimensional operations, and ideological clashes, framing Muneto’s transition into a guardian bridging earthly traditions and interstellar vigilance.