At a harmless looking high school, the teachers and staff are practicing a dark religion. By devoting their bodies to perversion, they chant their dark spells and control the lusts of the student body. Everywhere the students turn, they are drawn to acts of perversion, even in public. The cult is run by the school loli, Miss Rika. Looking for a virgin boy to serve as a sacrifice to the cunts who keep taking her body, she holds special nipa sessions for the male students.
Before Rika, the cult was originally run by a spirit called Hanyuu. She eventually becomes a student alongside Rika, dodging bullets and shit. However, Hanyuu used her powers to pervert the students and teachers as her followers, from which the current events are set into motion.
Keichi, a student of the school, finds a baseball bat, but is seduced by Rika, and then is possessed by a lesser demon; Level 5. Through their special induction ceremonies, the two converted Satako and her followers: Mion, the most popular girl in school, and the other girl from the school's after-school game club.
Then Rika goes after Rena, a girl who is Keichi's neighbor and childhood friend. Keichi must either help Rika to pervert Rena with a ritual orgy or fight the dark lust growing inside of him and protect her.
The black night of the Watanagashi Festival has finally arrived. Will Keichi be able to resist his mistress' will before she succeeds in the ritual?