Takeshi is a gloomy virgin university student who passionately loves the adult doujinshi series Karamizakari, memorizing every scene and line of dialogue. One day, he tries to rescue a female student who resembles his favorite character, Takeuchi-senpai, from a group of thugs. Instead, he is beaten and then hit by a truck. When he wakes up, he has reincarnated inside the world of Karamizakari as Takashi, the bald, notoriously promiscuous character known only as the "bozu." Initially disoriented, Takeshi realizes he now inhabits a character who is a skilled womanizer, a stark contrast to his former timid self.

Using his encyclopedic knowledge of the original story, Takeshi decides to follow the plot as closely as possible to navigate his new life. He successfully sleeps with Niiyama, one of the heroines, losing his virginity and gaining confidence. However, the moment he encounters his all-time favorite character, Takeuchi-senpai, the story begins to deviate from the original script. Realizing that his presence is changing events, Takeshi abandons the predetermined path and decides to pursue his ideal version of the Karamizakari world.

He starts a relationship with Niiyama, but the free-spirited heroine Iida relentlessly pursues him, eventually winning him over. As the summer vacation unfolds with trips to the beach and school events, Takeshi indulges in a hedonistic lifestyle. The narrative escalates during the cultural festival, where the two strongest male characters from the original series, Waki and Shunya, make an appearance, driving the story toward a chaotic and climactic conclusion. Over the course of five volumes, the series follows Takeshi as he rewrites his fate, fully embracing the wild, sexually charged adventure of his new existence.