Innsmouth resembles a semi-anthropomorphized octopus. His head resembles the mantle of an octopus and has two ridges leading up to his eyes. Innsmouth has no nose, and his mouth is at the end of a trunk-like structure with three suction cups on each side. On either side of the trunk, there are two fully prehensile tentacles that Innsmouth uses as an extra pair of appendages. His skin is a shade of dull red and is dotted occasionally with bumps and papillae, and acts as flexible webbing between his four arms. Said arms appear to be boneless, and have a suction cup at where the deltoid would be, the elbow, and the base of the wrist.
He wears a pair of red boots with pointed toes, a pair of baggy grey pants, a brown belt (presumably leather), and various watches and bracelets. His main accessory, however, appears to be the long, maroon sleeveless coat and red scarf that he wears as a hood of sorts.
From his short appearance in Episode 32, Innsmouth appears to be nothing more than a petty criminal motivated by greed. This showed that he was not afraid to take hostages and resort to underhanded tactics in order to further his own goals.
- Enhanced Strength: Innsmouth's Quirk may also give him enhanced strength, enough to pick up an adult with one arm and deliver a punch hard enough to break rock and dent metal.
Unknown Mutant-type Quirk: Innsmouth's Quirk appears to be a Mutant-type quirk that gives him the physiology and skills of an octopus, such as multiple presumably boneless, stretchy limbs, suction cups, and the ability to spit ink from his siphon-like mouth.
- Innsmouth's name and appearance seem to be a reference to H.P. Lovecraft's short story The Shadow over Innsmouth, as well as the Cthulhu Mythos.
- The design of Innsmouth's mouth seems to be based on breathing apparatus used by divers.
- Innsmouth is the franchise's first anime-exclusive villain.