Tsuna faces a group of assassins that's taken exception to his candidacy for the coveted position of boss of the Vongola Family. With recent experience having made their deficiencies in fighting prowess glaringly apparent, Tsuna's ""family"" members decide they need to undergo a serious training regimen in order to meet this new threat. It hardly helps that Tsuna, now possessed of an impressive new ability, needs the training more than anyone else!

Junior high student Tsuna is a failure at school, sports, and social life. He needs a Mafia hit man tutor like he needs a hole in the head...and he's about to get both!