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)