Kekkou Kamen is about the misadventures of a student named Mayumi Takahashi who attends a boarding school called Toenail of Satan's Spartan Institute of Higher Education that is run by sexual predators. The teachers are constantly looking for ways to torture or humiliate the students, and from this, the teachers derive sexual satisfaction. Takahashi's only protection is from a mysterious figure known as Kekkou Kamen.
Kekkou Kamen herself is a mysterious figure who hides the face but not the body! She fights evil with nudity, and nunchucks.