Teacher Ben serves as a faculty member at Sparta Academy under Principal Toenail of Satan, acting as a secondary antagonist across adaptations. In the original manga, he appears briefly as a biology instructor attempting to dissect Mayumi Takahashi's pet cat. When Mayumi intervenes, his twisted logic concludes only a cat would befriend another cat, leading him to target Mayumi for dissection instead. Kekko Kamen interrupts and defeats him, revealing him as overtly insane with mad scientist traits.

The OVAs significantly expand his role as Toenail of Satan's primary accomplice throughout all four episodes. He actively devises and executes punishments against students, particularly targeting Mayumi Takahashi for her academic performance. In OVA 1, he assists in her whipping and crucifixion on a swastika-shaped structure. OVA 2 shows him strategizing to defeat Kekko Kamen, including recruiting the muscular Shuwarutsu Negataro to exploit her perceived weakness. OVA 3 features him collaborating to create Hanako Tanaka, an android transfer student designed to monitor and punish failing students; he observes alongside the principal as Hanako attacks Mayumi with electrified tentacles. In OVA 4, he operates in a supporting capacity, suggesting targeting Mayumi to lure Kekko Kamen and later advocating for the punishment of student Yuka Chigusa.

Throughout the OVAs, Ben displays consistent characteristics: sadistic enjoyment in administering punishments, overt perversion including claiming to recognize all female students by their underwear scent, and unwavering loyalty to the principal. He faces repeated defeat at Kekko Kamen's hands, often via her signature finishing move.

Trivia notes indicate the character's given name is Kiyoshi, sharing the birth name of Kekko Kamen's creator, Go Nagai.