Nanba Deadend 

Nanba Tsuyoshi is leading a double life. He's part of a hardcore delinquent family, and he's supposed to go to their traditional Ichimatsu high school and be the top fighter. Instead, he's secretly attending the high-class Shirayuri high school, as a normal kid. For a while, things seem to be going well. He has the skills of a top fighter, so he just sneaks into Ichimatsu to knock out his competitors. Afterwards, he switches back to his mild-mannered, Art Club president, student council president alter ego. With a little help from a few trusted friends, he's kept the two lives safely separate. Everything gets a little harder when his little sister Ginko decides to attend Shirayuri high school. Will he be able to keep his identity secret from his own sister, as they attend the same school? And how will he deal with Yayoi, a Shirayuri student with a huge crush on his punk persona? Will he be able to keep up his double life through graduation?