15 Sai no Blues.

Sanada Kohei, a third-year junior high school student, is bullied by classmates and struggles with both school and family life. He finds solace in caring for potted flowers in his room. After going through ten tutors, Kohei meets Shunsaku, a hip-hop singer-turned-tutor. Shunsaku's unconventional and tough approach helps Kohei transform.