Muscle Devil

At first the Muscle Devil presents itself as a tiny one-eyed serpent, feigning frailty so that it seems harmless and exposed. When it works its muscles, that disguise drops away to reveal its true shape: a hulking, snake-like heap of skinless sinew studded with numerous eyes and a maw crowded with crooked teeth.

Cruel and crafty, the devil leans on deception to lower Denji's guard, even puppeteering a young girl's body to serve as its lure. Its loathing of humanity runs deep: it seizes the child to torment her and snaps Denji's arm simply to flaunt what it can do.

During the Introduction arc, Denji comes upon the Muscle Devil in the company of a young girl who pleads with him not to harm it, swearing the devil saved her from an abusive father. Torn by the scene, and recalling through Pochita that not every devil is wicked, Denji offers to let the three of them flee together. The instant his guard slips, the Muscle Devil grabs him and rends the muscle of his arm. It means to finish Denji and then amuse itself with the girl, but Denji becomes Chainsaw Man and shreds the devil to pieces. Its signature power lets it command any muscle it touches, wrecking a body through contact alone, and by flexing its own sinew it can balloon in size and might.