The Reborn! story revolves around a boy named Tsunayoshi "Tsuna" Sawada, who is chosen to become the Vongola Family's boss due to him being the great-great-great grandson of the first Vongola boss, who had moved to Japan from Italy during his time. Also, the other candidates for the position of the head of the Vongola Family died. For these reasons, Tsuna is the only remaining heir. As such, Timoteo a.k.a. "Vongola IX," the current head of the family, sends Reborn, an infant hitman from Italy, to train Tsuna. Tsuna then unwillingly undergoes training from Reborn. Reborn's main method of teaching Tsuna is the "Dying Will Bullet" ("Deathperation Shot" in Viz Media's translation of the manga), which will make the person be "reborn" with a stronger self intent on fulfilling his dying will. Through his experiences, Tsuna unconsciously becomes stronger and more confident, which ultimately makes him better suited as the Vongola Family's boss despite continuing to reject his Mafia inheritance.
Tsuna goes through many predicaments in his progress of becoming the Vongola boss including fighting against escaped Mafia convicts posing as Kokuyo Junior High students. Later, The Varia, a rival group of Vongola assassins, claim the right for their boss to be the true Vongola boss, and start a competition to decide it. To defeat the Varia, Reborn recruits most of Tsuna's schoolmates to become the Vongola guardians: Hayato Gokudera, a dynamite expert who wishes to be his right-hand man, Takeshi Yamamoto, a baseball player who thinks the Mafia is a game, Ryohei Sasagawa, the energetic captain of the school boxing club, and Kyoya Hibari, the deadly head prefect. Lambo, a weak infant assassin who came to kill Reborn, and Chrome Dokuro, a girl who has a mental and physical link with the criminal Mukuro Rokudo, joins them as well. After defeating the Varia, Tsuna and his friends are accidentally transported to the future where they must face the Millefiore Family, which is annihilating the Vongola.
CHARACTERS: Protagonist Tsunayoshi Sawada Main article: Tsuna Sawada
Tsunayoshi Sawada (沢田 綱吉/ツナ ,Sawada Tsunayoshi?), referred to as Tsuna, is the 14-year-old central character of the series. Because of his severely low self-esteem and lack of talent in any activity, Tsuna is known as "No-Good Tsuna" at his middle school Namimori. After being informed that he is the heir to the Vongola Family, due in part to him being the great-great-great grandson of the first Vongola boss as well as the untimely deaths of the other candidates for the position, he is trained into becoming a mob-boss by the infant Vongola hitman Reborn. Tsuna is often shot by Reborn with a bullet that increases his physical abilities in order for him to fulfill his regrets. That state is what gradually makes others see him in a better light. For the most part of the series, Tsuna rejects his position and wants nothing to do with the Mafia, however, due to the results of various conflicts involving himself and his friends, his own power matures and he eventually starts embracing his destiny. He is voiced by Yukari Kokubun in the anime.
 Hayato Gokudera Main article: Hayato Gokudera
Hayato Gokudera (獄寺 隼人 ,Gokudera Hayato?) is a 14-year-old transfer student from Italy who was placed in Tsuna's class. Gokudera is a dynamite expert nicknamed "Hurricane Bomb Hayato" (スモーキン・ボム 隼人 ,Sumōkin Bomu Hayato?). He keeps various explosives hidden on his person and uses those explosives liberally by lighting them with a cigarette (or several) held in his mouth. Initially, he comes to Japan in order to test Tsuna's strength, and after the latter risks his life to save Gokudera, he devotes himself entirely to Tsuna, having sworn to become his right-hand man. A hot-headed and short-tempered youth, he continuously gets into fights with several of the other characters, especially to those who try to get too close to Tsuna. Despite his personality, he is considered to be a genius, excelling in his academic studies. He is voiced by Hidekazu Ichinose in the anime.
 Takeshi Yamamoto Main article: Takeshi Yamamoto
Takeshi Yamamoto (山本 武 ,Yamamoto Takeshi?) is the 14-year-old popular baseball star of Namimori Middle School. Despite his carefree and outgoing personality, he initially has no confidence in doing anything other than baseball, even attempting to commit suicide after sustaining major injury to his arm. After Tsuna reassures him, the two become close friends, and Reborn tries to recruit him into the Vongola Family. He hardly takes anything seriously, and is usually oblivious to what is truly happening around him, often tricked by Reborn into participating in Mafia-related events because he thinks that they are all just playing a game. Though he becomes a dedicated and valuable member of Tsuna's family, growing to become a fighter who excels at swordsmanship, he still does not understand the full extent of the situation surrounding the Mafia. He is voiced by Suguru Inoue in the anime.
 Lambo Main article: Lambo (Reborn!)
Lambo (ランボ ,Ranbo?) is a cow suit-clad 5-year-old assassin from Italy affiliated with the Bovino ("Bovino" means "bovine" in Italian) Famiglia. He has a huge afro (which he stores a variety of objects in, such as snacks and weapons) with horns on the sides of his head. Despite being a hitman, he lacks the emotional maturity and discipline that Reborn has and is also very conceited as well as being a crybaby. In order to prove that he is worthy of becoming his own family's boss, he comes to Japan to kill Reborn, though he only proves that he is no match for the Vongola hitman. His main choice of weapons are hand grenades, and his future dream is to rule the world. He also possesses his family's Ten-Year Bazooka, which replaces his present self with another version of himself ten years into the future. The 15-year-old Lambo remains a crybaby, though his good looks make him more charming to others. His child self is voiced by Junko Takeuchi, while his older self is voiced by Kenjirō Tsuda in the anime.
 Ryohei Sasagawa Main article: Ryohei Sasagawa
Ryohei Sasagawa (笹川 了平 ,Sasagawa Ryōhei?) is the 15-year-old passionate member of the boxing club at Namimori Middle School. He constantly asks others he believe are strong to join his club, most notably Tsuna. In response, Reborn wants to recruit him into Tsuna's family. Every time he sees Tsuna and his family doing something strange, he gets fired up and always wants to be a part of it. Because of his energetic character, however, he does not understand the full extent of Tsuna's connection with the Mafia, but still does everything that he can to protect him and fights with as much spirit and confidence as the others. Proficient in hand-to-hand combat, his boxing training lead to his peak physical condition. He is a habit of always saying "to the extreme" as a single response or as an ending to his sentences. He is voiced by Hidenobu Kiuchi in the anime.
 Kyoya Hibari Main article: Kyoya Hibari
Kyoya Hibari (雲雀 恭弥 ,Hibari Kyōya?) is the leader of Namimori's Discipline Committee, or Prefects, whose members happen to be a group of delinquents loyal to him despite his lack of care for them. Though he mostly speaks in a calm tone, Hibari is an excellent but violent fighter himself, who uses a pair of tonfa as his primary weapons. Though he uses his status to harass others, he actually has great pride in his school and has a soft side toward animals. However, students are not the only ones who fear him, teachers and other town residents know of him as well since he enforces his form of order throughout the entire town. He prefers to be alone, usually beating up those who crowd near him. Despite caring little about the events surrounding Tsuna and his friends, Hibari takes a great interest in Reborn after seeing his abilities, which is reciprocated by Reborn, who wants to recruit him as part of Tsuna's own family. He is voiced by Takashi Kondo in the anime.
 Mukuro Rokudo Main article: Mukuro Rokudo
Mukuro Rokudo (六道 骸 ,Rokudō Mukuro?) is a 15-year-old Mafia criminal who escaped from an Italian prison, which held some of the most dangerous Mafia criminals, before he was to be executed. Not long after, he, along with his two subordinates, came to Japan, enrolled in Kokuyo Junior High, and started the Kokuyo Gang, which consists of heinous criminals whom have recently escaped from prison. Skilled in casting illusions as well as mind control, He attempts to take his revenge on the Mafia by taking over Tsuna's body and using him to wreak havoc. When his plan fails due to Tsuna's interference, he is once again imprisoned. However, later on in the series, after possessing the body of Chrome Dokuro, he takes on a more supportive role for the series' main characters, though still prefers to not want to associate with them. He is voiced by Toshinobu Iida in the anime.
 Chrome Dokuro
Chrome Dokuro (クローム 髑髏 ,Kurōmu Dokuro?), originally named "Nagi", is a 13-year-old Japanese girl who wears a Kokuyo school uniform. Mukuro Rokudo uses her as a vessel after he saved her life by creating illusionary organs for her when she lost her right eye and some of her organs in an accident. Chrome has been shown using two of Mukuro's six skills: creating illusions and summoning beasts that kill the enemy. The Japanese rōmaji of her name, Kurōmu Dokuro, is an anagram of Mukuro Rokudō.
Chrome is the named holder of the Mist Ring, and thus battles Mammon in the Vongola Tournament. When she is overwhelmed by Mammon's powers, Mukuro takes control and defeats him. After being transferred into the future, her physical condition takes a turn for the worse as several of her internal organs begin to fail. However, under adult Hibari's instructions, she uses the power of her Vongola Ring to sustain her organs via her own illusions, thus avoiding any immediate danger. She later takes part in the raid of the Millefiore Family's main base. She is voiced by Satomi Akesaka in the anime.
Antagonist Kokuyo Gang Main article: Kokuyo Gang
The Kokuyo Gang is a group led by Mukuro Rokudo, who formed the group after escaping from a special, high security jail in Italy which housed heinous criminals who have even committed crimes against the Mafia. Along with the two comrades he escaped with, Ken Joshima and Chikusa Kakimoto, he recruited other Mafia criminals who were able to break out from the same jail some time later. After their defeat at the hands of Tsuna and his friends, they were all once again imprisoned, though Chikusa and Ken are later able to escape, while Mukuro strikes a deal with the Vongola for their safety.
 The Varia Main article: The Varia
The Varia is the Vongola Family's elite, independent assassination team. They are composed of genius assassins who work in the deepest recesses of the Mafia. Each member takes on missions that are said to be impossible to accomplish by humans, however, they do not accept a mission unless they believe there is a 90% chance of success. Those that see them work often say that their high level assassination skills are demonic. Despite lacking loyalty and respect for other members, they are extremely loyal to their leader, Xanxus. The Varia also appear to have more than fifty subordinates ranged under the command of the main members. The Varia is apparently reclusive, only showing themselves after Iemitsu Sawada disappeared.
 Millefiore Family Main article: Millefiore Family
The Millefiore Family (ミルフィオーレファミリー ,Mirufiōre Famirī?) is the Mafia family that is engaged in battle against the Vongola Family in the future. The Millefiore is a result of the merging of two separate Mafia families: the up-and-coming Gesso (ジェッソ ,Jesso?) Family led by Byakuran, and the family with as much history as the Vongola, the Giglio Nero (ジッリョネロ ,Jirryo Nero?) led by Uni. They are organized into two groups to distinguish their old families, which are then further separated into 18 different squads, each named for a plant or flower. Those originally from the Giglio Nero are the Black Spell and have the tendency to engage in direct combat, while those from the Gesso are the White Spell and specialize in cunning battle tactics. There appears to be animosity between members of the White Spell and the Black Spell, resulting in a lack of communication and sabotage by individual squads. Their organization also possesses the Mare Rings, a set of seven rings on par with the Vongola Rings originally belonging solely to the Giglio Nero.