In a world reminiscent of Earth, Serian is home to two high school students, Yagi and Okami, who harbor dual identities - Yagi as the confident sadist 'Goat' and Okami as the fierce delinquent 'Wolf'. As their mating season approaches, Yagi's desires become uncontrollable, leading to a day where his advances turn forceful. Meanwhile, Okami's lewdness surpasses even that of a beast, causing astonishment. Once close friends, their relationship now simmers with constant conflict. Amidst their infiltration training on Earth, complications arise when Yagi experiences unusual reactions during his mating period. Concerned, Okami attempts to intervene, only to find himself bitten on the nape in a startling turn of events.