The story begins with Sawada Tsunayoshi, or Tsuna, an average boy who often gets picked on for his poor performance in sports/school/life in general. He returns home from school one day to find that his mother has hired a home tutor to boost his grades. However, the home tutor is actually a hitman by the name of Reborn sent to prepare Tsuna to take on the role of the 10th mafia boss of the Vongola family - something Tsuna has no interest in being a part of.
Sawada "Tsuna" Tsunayoshi: The manga's reluctant protagonist. Although appalled by the idea of entering into the mafia, with help, encouragement, and the occasional death threat from Reborn he begins to grow into his pre-determined role, whether he likes it or not.
Reborn: The legendary Italian hitman respected by the vast majority, if not all of the mafia world. Though he appears not much older than a baby, he is unmatched in skill by his fellow assassins.
Gokudera Hayato: An intellectually gifted, dynamite wielding member of the Vongola family who traveled to Japan to test Tsuna's worthiness of being the next boss. He eventually dubs himself Tsuna's right hand man and, although his over-zealousness sometimes causes more problems than it solves, assists him through all of the various trials he encounters.
Yamamoto Takeshi: A good natured, optimistic guy labeled by Gokudera as a "baseball-freak", he befriends Tsuna despite his good-for-nothing reputation and eventually becomes part of the Vongola family, which he believes is an intricate mafia role-play.
The most recent chapter (284) of the manga can most likely be found on your favorite manga-hosting site. A new arc has just begun! For those that read the manga, who exactly do you think the new transfer students are? For those that don't, hopefully you'll put it on your list~