Middle school student Tsuna has always gone through life in last place; but when he learns that he is getting a tutor to help him raise his game, he had no idea that his benefactor would turn out to be... an infant and a mafia hitman?! As if things can't get much stranger, Tsuna then discovers that the powerful Vongola family has chosen him to be its next successor - a position that has control over all mafia families. Joined by friends Tsuna unwillingly starts out on his path to becoming a mafia boss - if he can survive the training!
Both Reborn! and Nuraihyon no Mago have a similar feel between them. They both are about young and weak boys becoming the next head of a top mafia family (Reborn of the human world, and Nuaihyon of the demon world). They both have personality changes, respected older "brothers" to guide them, and a lot of action. But putting all of that aside, they just remind me of each other, between the plots and rivals, and all the lives at stake. If you like one, you should give the other a try.