Tatsuya Kubo, a biology teacher at Yayoi Mizuno's school, marries the popular instructor known for her devoted student fan club. The couple hosts a summer camping trip at a lakeside forest, serving as both a vacation and farewell gathering for Yayoi, attended by her former fan club members.

During the excursion, a violent storm forces the group into the forest's interior, separating the students from Tatsuya and Yayoi. While foraging, several students encounter a stranger distributing a supernatural nectar that triggers overwhelming lust. Kyoko and Shiori locate a cabin with provisions and reunite with Tatsuya. After Shiori departs to fetch the others, Tatsuya engages Kyoko in a sexual act, coercing her into oral sex followed by intercourse. Yayoi witnesses the encounter unnoticed, undergoing internal changes afterward.

The trip spirals into terror when the group discovers a cave housing the Garanta, a carnivorous plant-demon. This entity assaults them, inflicting sexual torture to advance its cross-breeding agenda.