The mafia underworld is ruled by the strongest people in the business, the Italian Vongola family. Vongola's current head, the ninth head, is an old man ready for retirement. But before he can step down, he needs help from a professional hitman to prepare the next next head of the family for the world that awaits him.Sawada Tsunayoshi is an ordinary teenage boy who attends Junior High, who is unpopular, has no friends and is desperately in love with a girl from his class. But Tsunayoshi's life takes an extraordinary turn when he meets Reborn, an infamous hitman, who has been sent by the Vongola boss to prepare Tsunayoshi for his future as a mafia boss!