Sixteen-year-old Inari Anamori, a boy who adores animals, transfers to a new school and on his very first day is attacked in the forest by a bizarre, unknown creature. He is rescued by Gunze Arabaki, a mysterious and misanthropic loner with an inexplicable disdain for people. This chance encounter throws Inari headfirst into a chaotic and absurd school life. Gunze is a member of PETS, a secret underground organization dedicated to protecting creatures called Mesos—mysterious beings with strange and often dangerous abilities. Inari soon joins PETS and, alongside Gunze, is thrown into a series of incidents caused by the Mesos, each more surreal and comedic than the last. The duo must handle crises ranging from mischievous Mesos wreaking havoc at school to larger threats that test their resourcefulness. As Inari navigates this bizarre new world, he encounters other PETS members, including a colleague named Kosha, and faces missions that reveal the growing complexity of the Mesos phenomenon. The series blends offbeat gag comedy, bizarre creature designs, and escalating absurdity, all while hinting at deeper mysteries behind the Mesos and the true nature of the enigmatic Gunze Arabaki.