Ryouzanpaku History's Strongest Disciple

Tatakae! Ryouzanpaku Shijou Saikyou no Deshi, relates the story of a peaceful yet weak boy, who one day, after being beaten up really bad by some of his school comrades, decides that being bullied around isn't an option anymore. Seeking revenge on his bullies, the young boy, Shirahama Kenichi, decides to join a fighting dojo. But what he doesn't know is that the dojo he wants to join is actually a place of gathering for those who have mastered different types of fighting styles. Thus begins his journey.
This is the original version that History's Strongest Disciple Kenichi is based on.