Evil Heart(2005)

Evil Heart

Masaki Umeo is a middle schooler with a nasty temper. Because of his temper, he is causing all sorts of problems and is constantly involved in fights causing his sister to worry about his well-being. One day, he stumbles upon an Aikido class which he becomes interested in, but soon dismisses it until he meets Daniel- an english teacher from Canada. Daniel teaches Umeo about the way of Aikido in hopes of giving Umeo a different outlook in his life, but it isn't that simple because there is a dark reason behind Umeo's temper...

(Source: Hidoi~! Translators)