Shūhei Murosaka, Ryouka Tsurumi's childhood friend, is confined with her in a quarantined apartment building besieged by the lethal entity X. Sporting brown spiky hair and matching eyes, he consistently wears a gakuran uniform. His core mission revolves around helping Ryouka evade recurring assaults by X—a creature that manipulates humans into supplying blood for its reproduction. Shūhei repeatedly shields Ryouka during X's attacks, displaying fierce protectiveness despite near-impossible odds. Both ultimately fall prey to X’s hypnotized thralls, leading to their consumption by the entity. After each demise, Ryouka restarts in a time loop where Shūhei reappears. Together, they confront X’s evolving manifestations across repeated cycles, strategizing to uncover an escape route that shatters their grim fate of capture and devouring.