Masaru Charai is a high school freshman who attends Hamedori Academy. He spends his days in debauchery with his friend Tenga Kiryu, who can’t even sit in class properly. Naturally, everyone around him thinks that he’s the worst. One day, Masaru suffered an injury to the head and learns that he was actually in a game world…… The only thing Masaru has over other people is the size of his “tool”. And on top of that, he’s in an environment where he’ll get to constantly stick it in the “heroines” of this world── This is the story of Masaru using his “tool” to overcome his school struggles even though he isn’t the protagonist of the ero game world.