The series tells the tale of a young martial artist who transforms into a bizarre hero of justice by wearing a pair of panties on his head.

Kyōsuke Shikijō is a high school student skilled in kenpō, but incompetent with girls to the point that his interaction with them gets him into painful situations.

When she is taken hostage by a group of criminals during a bank robbery, Kyōsuke is forced to take a disguise to save her without being recognized by the crooks after an earlier incident where he reveals himself on a megaphone.

When he accidentally puts a pair of panties over his head instead of a normal mask he undergoes a transformation: due to the perverted genetics of his mother (an S&M worker), he is able to awaken the full potential of his body.

Running out wearing nothing but the panties on his head and underpants covering his loins, Kyōsuke, now christening his masked self Hentai Kamen, uses his power and perversion to defeat the criminals and save Aiko.

The series returned by way of School Rumble author Jin Kobayashi with the special one-shot Kaettekita Hentai Kamen (帰ってきた変態仮面, lit.