Suiko is a water demon kappa recruited and mechanically enhanced by Eko to aid in overthrowing human control of Shinjuku. Operating under the human guise of a professional wrestler, he uses this cover to maneuver within the city. For sustenance, he hunts humans, draining their blood in public restrooms and exhibiting a preference for female prey.

His combat abilities focus on hydrokinesis, manipulating water as a weapon. He also summons and commands the spirits of his slain victims, deploying them as spectral allies during conflicts. As one of Eko's mechanized Mikura forces, Suiko participates in systematic Shinjuku attacks, furthering Eko's campaign to dominate the city through orchestrated violence and terror.