Katekyo Hitman Reborn

The plot revolves around the life of a young boy named Tsunayoshi Sawada, who is not good at sport and study and he finds out that he is next in line to become the boss of the most powerful Mafia organization called Vongola, the Vongola Family. As such, the Vongola's most powerful hitman, a gun-toting infant named Reborn, is sent to tutor "Tsuna" on how to become a respectable boss.