Sawada Tsunayoshi, or Tsuna, is a boy who is not good at ether study or sports. To him, a tutor named Reborn is sent. Surprisingly he is a baby, and his purpose is to make Tsuna a full-fledged boss of an Italian mafia, Vongole Family. The way Reborn teach him is to shoot "Deathperation" bullet into Tusna's head. Those who are shot by the bullet are "reborn" to work hard to fulfill his dying will.