The war is over, and hero Dias is finally rewarded with land of his own—only to discover it's a barren frontier with no people, no villages, and no sign of civilization. With nothing but endless grassland ahead of him, Dias sets out to build a domain from the ground up. But after meeting Alna, a mysterious girl with a blue horn, his lonely frontier is about to spring to life.

Tsuna, a timid junior high student, is a failure at school, sports, and social life. But everything around Tsuna has been completely changed when a baby called Reborn, who claims to be an Italian hit man from Vongola family shows up! Reborn was sent to groom Tsuna for his future life as a mafia boss of the family!