Moriyama acts as aide to Major Yoshinobu Maeda upon assignment to Tokyo, operating within Special Forces Unit 16. Under Lieutenant General Nakajima's directive, he greets Maeda at Tokyo station and accompanies him to Tsukishima to assess captive vampire Misaki—an actress transformed during a stage accident. During preliminary evaluations, Moriyama voices a comparatively lenient perspective on Misaki's threat level, diverging from Maeda's guarded stance.

He engages in follow-up missions targeting associates of recent vampire attack victims. During an operation, Misaki breaches containment and assaults personnel; Moriyama sustains a bite during the struggle, contracting vampirism. This injury presents two grim outcomes: agonizing demise from transformation rejection or eternal vampiric existence severed from human ties.

Confronting this reality, Maeda executes Moriyama to spare him protracted suffering from transformation failure and to prevent a concealed vampire life that would irrevocably isolate him from his new wife and potential offspring. Moriyama's narrative concludes in the second episode without reappearing in later arcs or supplementary media.