Suwa, a vampire transformed during the Azuchi-Momoyama period at age 14–16, retains only fractured memories of his human past—flickers of childhood play near the Suwa shrine, which later inspired his name. To control his bloodlust, he dons a scent-muffling mask and bears eleven stigmata etched into his skin, permanent emblems of his curse.

A stealth operative in the military unit Code Zero, he eliminates rogue vampires with lethal efficiency, earning the moniker "the vampire who hates vampires." His contempt stems from centuries of self-loathing and the trauma of his transformation, when a swarm of vampires attacked him, leaving psychological wounds as enduring as the physical scars.

White-haired and perpetually masked below the eyes, he wears a black uniform lined with crimson, his youthful facade contrasting a weary, ancient demeanor. After Code Zero dissolves, he retreats to New York with Ayame, a companion, attempting to abandon his past while navigating immortality’s burdens.

Though pragmatic and detached, traces of humanity surface in morally gray choices—such as seeking solace with Akesato, a Yoshiwara prostitute, for companionship devoid of intimacy. These moments underscore his unending struggle: a clash between clinical duty, survivalist resolve, and the faint, persistent echoes of the mortal boy he once was.