Kumo Otoko is one of the original eight demons who served the wind demon Fuujin and was reincarnated by taking the body of a spider, giving him the appearance of a humanoid spider. He acts as the right-hand man and unofficial sidekick to the antagonist Takeshi Onimaru, a position he attains less through merit and more because no better candidate is available at the time. Onimaru often sends him on errands such as recruiting new warriors, gathering intelligence, and carrying out schemes against the protagonist and his allies.

In terms of personality, Kumo Otoko is defined by a sharp intelligence that he consistently undermines with a goofy, clumsy nature. He creates genuinely clever and complex plans, but his own buffoonery almost always causes them to backfire in comedic fashion. Despite this, he is fiercely and unwaveringly loyal to Onimaru. He never displays genuine malice or ill-will toward Yaiba and his companions, and he is routinely mistreated by his master without ever considering betrayal. This unusual combination of traits makes him the only member of the original eight demons who stays at Onimaru’s side until the very end, while the others are either defeated, killed, or switch allegiance.

Kumo Otoko’s abilities reflect his spider host. He can shoot powerful strands of webbing to ensnare or strangle opponents, and he can launch darts from his mouth that contain enzymes capable of liquefying a target on contact. His role in the story is that of a persistent, often humorous secondary antagonist whose loyalty grounds Onimaru’s forces even as other demons fall away. Although he is part of the villain’s ranks, his lack of real malice and his comedic failures soften his antagonism, positioning him as a figure who is more pitiable than threatening. His development is minimal in the sense that he remains consistently devoted and accident-prone throughout the story, but his steadfast presence becomes notable precisely because he outlasts the rest of the demon cohort through sheer, almost dog-like fidelity.