Box! (2010)

When high-school student Yuki is rescued from some street toughs on a train by Kabu, they realize that they were childhood friends prior to Yuki moving away. Reunited, Kabu convinces Yuki to join the high school boxing club, and eventually compete in regional tournaments. The most feared boxer in their weight division is Inamura, and it is only a matter of time before one (or both) of them must face him.