Hajime no Ippo (Fighting Spirit) [Manga]

From Baka-Updates Manga:
Throughout his childhood, Makunouchi Ippo has always been picked on by his fellow classmates. Long hours helping his mother run their family business, a fishing boat store, has left him without the time to make friends, and so he remains an introverted loner, doomed to be beaten day in and day out. Although he hates being bullied, he hates himself even more for not being able to fight back against his tormentors.
“What is it like to be strong?” he asks himself as he stares at his clenched fist. “I want to be strong.” His encounter with Takamura Mamoru, a professional boxer, leads to the discovery of a dynamite punch that opens up the doorway to a whole new world where that dream can become a reality. At the Kamogawa Gym, Ippo now trains with the aspirations of becoming a professional boxer and discovering what it means to be strong.