KenIchi: The Mightiest Disciple OVA

The protagonist of the tale is 15-year-old high school student Kenichi Shirahama, a longtime victim of bullying. He befriends Miu Frinji, a transfer student, early on in the novel. Wanting to learn more martial arts, he decides to follow her to Ryzanpaku, a dojo where her grandfather Hayato Frinji and other masters of other martial arts train. After learning the fundamentals from Miu, Kenichi defeats a senior member of the school's karate club and turns into a target for all the school's miscreants. While first practicing self-defense, Kenichi gradually turns into a full student of Ryzanpaku and develops feelings for Miu. Following then, Kenichi's daily activities are split between his training with the Ryzanpaku's six masters and his battles with the bullies known as "Ragnarok," who alternately strive to recruit and defeat him.