At a high school in Tokyo, several of the female students have been moon-lighting as prostitutes. A teacher catches onto this fact and goes about putting an end to it. Things go awry when he discovers he turns into a sex demon with tentacles whenever he gets aroused (huh?). He turns from savior to vilifier, poor prostitute school girls.

This slice of shot-on-video hentai horror kicks off with a crazy old woman stealing what looks like all-butter shortbread from three statues wearing red hats. This causes an earthquake which releases ancient demon spores from a cave into a nearby pool of water. Unfortunately, this pool is precisely where a lesbian professor—part of a group of students and teachers who are spending a few days camping in the woods—decides to refill her water canteen. She accidentally ingests the spores, which causes the eruption of huge, thrashing, veiny, slime-covered tentacles that seek out new victims and enter the nearest orifice, thus allowing the demon to pass from host to host.

Manami, the sole survivor of Angel of Darkness 2, is rushed to hospital where she slips into a deep sleep. A priest correctly suspects that the demon (now referred to as an Injuu) is inside Manami's body, but by the time he is able to confirm his theory, the creature has already moved on. As before, the tentacled beastie passes from host to host (by thrusting its slimy appendages into its victims' orifices), eventually ending up inside goody-goody schoolgirl Fumie, who does her best 'Linda Blair' impersonation for a while, before the priest inevitably turns up to save the day.

This time around, the demon is trapped inside sexy but wholesome schoolgirl Izumi, but is unable to get up to its usual tricks (rampant orifice invasion) thanks to the crucifix that she wears around her neck. Out to locate and destroy the monster are a nun and a priest, but their efforts are hampered by Izumi's evil protector Sakiko, who does her best to help the girl realise her true tentacle-thrashing potential (and, in a Carrie-style side story, also settle the score with a group of nasty school bullies who have been making Izumi's life hell).

College life getting you down? Switch to Seika College where the students are getting a whole new lesson in sexual education! Michiru's classes were dull and boring until her classmates, Chie, Saori and Takeru, started taking extra classes at a new night school. Utilizing subliminal messaging, the school helps their students ace their daytime college exams. Unfortunately, the school's professor forgot to mention the process has a few sexual side effects... The next day Saori's in for the sexual education of a lifetime! Classmates begin masturbating, her professor is fondling the other students before her eyes, and Saori is getting so hot she's literally exploding! Then, on the way home, Chie finds her sexual appetite soaring. She'll take any man, or thing, that can relieve her inner burning desires! Can innocent Michiru uncover the truth behind the evil night school and the mysterious deaths of her friends before anyone else dies? Or is she fated to become another victim?