Mangas

3rd year middle schooler Sen Tobishima, who has inherited his late father's red hair and amazingly strong body, fails every class and cannot graduate to high school because he spends all of his time doing stupid stunts. His mother and grandmother have grown tired of his reckless behavior, so for summer break they have sent him to the kick boxing gym of Coach Sakurawada, the main who straigtened out Sen's father years ago.

This manga deals with the history of a teenager, Tobi Shima Sen, who lost his father and lives with his mother. He is a scrapper but his mother has no authority over him. In order to educate him, she decides to send him to a kickboxing coach during the holidays/vacation.

From MangaHelpers:Growing up, Wataru and his younger brother have both done gymnastics, much like their parents. At first, Wataru, being the older brother, could out-perform his younger sibling in the sport, but everyone quickly came to notice the large gap in talent between the two brothers. Now, his younger brother has been nominated to represent Japan in the Olympics, while Wataru lives his day-to-day life not knowing what to strive for. Wataru began attending a kick boxing gym, initially to just relieve stress. With the help of his gym mates and rivals, he begins to understand that hard work can surpass talent in the realm of kick boxing.