Enma Kozato  is a rather gloomy and introverted transfer student to Namimori Middle School. His social skills are poor at best; his shy demeanor and quiet voice make him an easy target for bullying. He appears to be weak-minded, even to the point that Hana Kurokawa describes him as "the type who'd get teased a lot" and reminding Tsuna of the way he used to be (and, in many aspects, still is). His red eyes have a symbol very similar to the crest on his ring.   ~!Later, It's revealed that he is the leader of the Shimon Mafia Family.!~  He is voiced by Uchiyama Kouki in the Katekyo Hitman REBORN! VOMIC.

Sawada Tsunayoshi is regular boy who has never excelled in sports, school or social life, thus being named "No Good Tsuna". Everyday, he leads just a normal life, living with his mother, while his father is away for work. But the thing Tsunayoshi doesn't know is that his family is actual lineage of the great Mafia Boss, the first head of Vongola, Giotto. 
Because of the Sawada history, Tsuna has been chosen to become tenth head of the Vongola family, an infamous Italian mafia family which rules the Mafia world. To become worthy of the title, Tsuna is being aided by professional hitman and infant, Reborn, who takes the role of Tsunayoshi's mafia tutor. 
(Source: Katekyo Hitman Reborn! FC)
 
Note: Chapter count includes two extra collections of short chapters published in volume 42

Vongola GP (Gran Prix) is spin-off series of Katekyo Hitman Reborn!, made by Takayama Toshinori. 
Manga introduces Tsunayoshi Sawada, called No-Good Tsuna who is descendant of world's legendary racer, Primo and his side-kick Gokudera Hayato. They battle on various members from the original Katekyo Hitman Reborn! plot.