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.
After Selkie is captured, Sirius and Froppy go after a boat that has stolen cargo. Once on the boat, the two of them are attacked by Innsmouth. Sirius is taken hostage by Innsmouth and tells Froppy that he'll give her back once he's free of the Coast Guard. Sirius gets a call over the radio but Innsmouth orders Froppy to tell them that they couldn't find the stowaways. Froppy goes against Innsmouth's wishes and tells them over the radio that the stowaways are at Double Rock. This upsets Innsmouth and he attacks Froppy with the intent to kill her. Froppy evades him but when she tries to rescue Sirius, Innsmouth grabs her by her tongue and pins her to the ground. It looks like it's over for Froppy but then Selkie arrives and saves her. Selkie and Innsmouth go head to head but Selkie wins the fight after delivering a mighty kick to Innsmouth's face. Innsmouth and his brothers are arrested and all the illegal drugs that they attempted to bring in are recovered.
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.
Octopus: Octopus is a Mutant-type quirk that gives Innsmouth the physiology and natural abilities of an octopus; presumably multiple limbs that are boneless and stretchy, 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.