Bakudan! - Bakumatsu Danshi

Despite his short stature and his cowardly personality, Eisaku Yazawa dreams of one day becoming a gang leader of a nation of thugs. As he starts high school, he ends up meeting several delinquents who attend the same school as him.

7 years have passed since the OZ gang was disbanded. The high school student Hoshino Eita is made to dress and work as a hostess called "Eira" at his family's establishment. While out in disguise, he encounters his classmate Miyabi Yamamoto. She inherited the banner of the OZ and "Eira" soon earns her trust. Now they're off to begin a new legend!

After being bullied at his old school, Makoto wants to be the main character of his own story. When he finds a bill with his face on it on a school trip to Kyoto, he takes it as a sign, which leads him to fall into a river. Once he comes to, he realizes that he has been transported back to the period of time in Japan known as the Bakumatsu!