Reborn!

Tsunayoshi Sawada, known to everyone at school as Useless Tsuna, is bad at studying, bad at sports and bad at talking to the girl he likes. Then a baby in a fedora arrives at his door: Reborn, the world's greatest hitman, sent to train Tsuna as the next boss of the Vongola, one of the most powerful mafia families in Italy. Reborn's teaching methods involve live ammunition and very little patience. Soon Tsuna's life fills with eccentric friends and would-be guardians: a hot-headed bomber, a cheerful baseball player and a dangerous prefect among them, along with rival families who want the Vongola's power for themselves. Akira Amano's series begins as a riotous school comedy and grows into an action saga of rings, flames and loyal friends, as a reluctant boy learns that strength means protecting the people around him. It ran in Weekly Shonen Jump for eight years and was adapted into a long-running anime.