Character Outline

Tsuna is a 13 year old boy who is set to become the tenth generation boss of the Vongola crime family.
In school, Tsuna has been given the harsh nickname of " No Good Tsuna ", as he is very clumsy and somewhat of a pushover.
Although he is the tenth generation Vongola boss, Tsuna is unwilling to take part in anything that has to do with the Mafia . He always denies the fact that he is a future Mafia boss and tries to avoid anyone involved with the Mafia. Tsuna is often surprised and horrified (for a comedic effect) at Reborn's and other mafiosos' actions. Later, even though he still wants nothing to do with the Mafia, he is grateful for the friends he has made since meeting Reborn. He cares a lot for his new 'family' and would put himself in the way of danger in order to protect them.
There have been many parralels that link Tsuna with the first boss and founder of the Vongola family, Giatto. Both of their personalities are likely to be very similar as it has been shown that they have similar goals and ways of standards.

History

Tsuna is a junior-high student and the Vongola Family's mob-boss -in-training. The reason Tsuna was recruited is because he is the great-great-great grandson of the first Vongola boss, who had moved to Japan a long time ago. Also, the other candidates, for the position of the head of the Vongola Family, died.

Before Reborn finds Tsuna, Tsuna is known as " No Good Tsuna " for his poor grades, bad luck, and lack of athleticism. When Reborn shoots him with the Vongola Family's Dying Will Bullet (a.k.a. Deathperation Shot), he comes back as a powerful mostly-naked (his boxers somehow survive) warrior with a flame on his forehead and blanked out eyes. However, this will only work if he has some sort of regret at the time Reborn shoots him (e.g. not telling Kyoko Sasagawa that he likes her). After five minutes, he turns back into his normal self, usually embarrassed by the fact that he's out in public with only his boxers on.

Synopsis

Introduction Arc

During the Introduction Arc, also known as the Daily Life Arc, Tsuna first meet's Reborn and learns of his heritage and destiny to become the tenth generation boss of the Vongola crime family. At first, Tsuna is reluctant and dismissive, but he soon learns that this may help him protect his friends, or, as Reborn calls them, his "family".
Reborn introduces Tsuna to the Dying Will Bullet. Tsuna also meet's his eventual "family" , who are mostly people from school, along with some future allies. Each member is introduced quite comically and usually brings Tsuna more frustration then hope and stability.
During the arc Tsuna endures everything from meeting other prominent mafia members, to learning how to swim, to nearly dying countless times.

Kokuyo Gang Arc

During the Kokuyo Arc, Tsuna is the true target of the gangs advances but does not realize this untill Reborn points it out. During the arc Tsuna is hit with the first Rebuke Shot allowing him to use Hyper Dying Will Mode as well as the X-gloves. Both the Rebuke Shot and the X-Gloves were created by Leon espacially for Tsuna and are part of Reborn's plan to slowly give Tsuna an identity and the ability to use the power Reborn knows Tsuna has.
Mokuro had previously tried to beat Tsuna by possesing his friends but with the new power Tsuna has gained from his Vongola blood he rises to the ocasion. He fights his possesed frineds by keeping his gurad up and thereby draining their strength. He uses his intuition, granted to him by his Vongola blood, to strike his friends down with a single hit, thereby temporarly paralyzing them and removing them from danger. He leaves them in the capable hands of Reborn inorder to finish Mokuro. Tsuna then procedes to defeat Mukuro in a brilliant battle that showcases Tsuna's growing strength and the power that he truly possesses.
In the aftermath Tsuna learns of Mokuro's troubled past and the secret behind his amazing abilities. He also meets Vindice who take the gangs members away for their eventual punishment. Tsuna then feels the effects of the Rebuke bullet and falls into a deep sleep to replenish his depleated energy.

The Varia Arc

During a peaceful visit to the mall, Tsuna encounters Basil, a young operative from the Vongola Family, and receives the half Vongola rings from Dino, as those Basil had were fake and a diversion. Tsuna is horrified as Reborn tells him about the history of the rings and the battle that will follow. He returns home to find his father and becomes even more depressed, as they have a very difficult relationship.
Tsuna receives the ring of Sky and is horrified to know that the other six rings were given out. Reborn is Tsuna's home tutor for his battle and Basil aids him in surpassing the zero point barrier that one the first Vongola boss could do.
Tsuna was very upset to hear that his friends had been sucked into his conflict with the Varia. He was especially concerned for Lambo, who is too young and tries to get him out of it by reasoning that he is already part of another mafia family. Reborn consoles Tsuna and tells him that the Bovino family was honored to have Lambo become part of the Vongola family. Reborn also tells Tsuna that while the ring guardians are usually drawn from within the family it is not unknown for them to come from outside the family, or the mafia altogether. Reborn also tells Tsuna that only he and the first boss had such unorthodox families.
Tsuna was scheduled to battle against Xanxus for the right to become the holder of the Ring of the Sky, and therefore be the next Vongola boss. However, during Lambo's battle against Leviathan, Tsuna was forced to intercede in order to save Lambo. Due to this interference, he forfeited his right as the holder of the Ring of the Sky. However, Xanxus agreed to hand over the rings to Tsuna's family if they took the lead by the end of the scramble for the rings.
Later, Tsuna's family obtains a 4 to 3 lead, however, Xanxus chooses to frame Tsuna for the "assassination" of the 9th, later we find that the 9th survived the attack. Xanxus then chooses to hold one last formal battle, having their family wear a special watch which poisons them, immobilizing them. They are required to retrieve the rings from pedestals and the rings themselves, when scanned by the watches, causes an injection of the antidote. Tsuna worries about his family for the first portion of the match, until he learns that Hibari managed to resist the poison and cure himself, then helping Gokudera retrieve his ring, managed to relieve Tsuna of his worries of his teammates possibly dying.

Future Arc

The future arc begins with the mysterious disappearance of Reborn while Tsuna and his "family" celebrate their victory against the Varia and Tsuna officially becoming the tenth Vongola Boss. Later, Tsuna is unexpectedly transported 9 years and 10 months into the future. Tsuna awakes inside a coffin, belonging to his future self.
He is then met by a future version of Gokudera, who is hovering over his coffin, mourning. After he apologizes to Tsuna for 'letting him down', he warns Tsuna about Shoichi Irie and tells him to kill him as soon as he gets back to the past. Unfortunately, as Gokudera is about to reveal why Tsuna was in the coffin, he is replaced with his younger self. They wander until they meet an older Lal Mirch , who at first tries to kill them, and later, an older Yamamoto. They bring the two to the secret underground Vongola base that the older Tsuna had built. Here, Tsuna's fear is confirmed as he is told that in this timeline, he is indeed dead. In later chapters it is revealed that he was viciously gunned down in public.
The fact that Tsuna, Reborn, and Gokudera have yet to return to the past dawns on them, and they are forced to seek a solution. We also learn that the Vongola family is at war with the Millefiore Family for unknown reasons. The war has nearly reached its conclusion, as almost all of the Vongola family and their allies have been killed. Tsuna also learns that his future self destroyed the Vongola rings, supposedly to stop the bloodshed over them, but this is merely a theory. Apparently, the Millefiore Family has stolen most of the other, lesser Vongola rings to use in their campaign against the family. Reborn states that the 7 guardians must be assembled immediately.
It is decided that the strongest of the seven guardians, Hibari, should teach Tsuna. Unfortunately, no one knows where he is, forcing Tsuna, Gokudera, and Takeshi to leave the base to find him. On their way, they meet the future I-Pin and Lambo, who are being attacked by two members of the Millefiore family. Tsuna finds the future Haru and Kyoko in the rubble, but within just a few minutes of finding them, they are replaced by their younger selves. Tsuna purifies his flame with the Ring of Sky and is somehow able to freeze Tazaru's flame. Tazaru is quite shaken by this as he repeatedly said that it was impossible, and comments that his opponent reminds him of the renowned 10th boss of the Vongola Family. Battered and beaten from fighting the two Millefiore mafiosi, Gokudera is able to use his Vongola ring with its box and fight back. Tsuna reawakens in the base's med center, having passed out soon after his victory. Tsuna seems to now be fitting into his future role as a Mafia boss better as he takes charge of the situation and demands action of Reborn instead of passively following his advice as he would have done normally. He sees his future path of getting home as hard, but he refuses to back down from the challenge or the hard work he must put in to achieve it. He is taking more charge in the family and seems to be slowly fitting into his new role.
Hibari later agrees to be Tsuna's home tutor and help to train him for the battle with the Millefiore Family. During their training Tsuna is trapped in Hibari's special spike ball, which is actually a hedgehog. Inside Tsuna sees visions of the Vongola Family's ancient and bloody history. He hears voices telling him that he must accept their history if he is going to be the next Vongola boss. However, Tsuna states that he would rather destroy the Vongola Family and reject the power he seeks than accept that their bloody history is his future. It is then that all nine of the previous heads of the Vongola Family appear before him. Because of his determination, Vongola I and the others approve of him, after which he breaks free of the spike ball, stunning the others (except, of course, Hibari) and revealing Version V.R. (Vongola Ring) of the X-Gloves.
Breaking free from the spiked ball Tsuna's dying will flame is more powerful then ever. Even though Hibari still beats Tsuna he demonstrates good control of his new power and a much keener mind. At one point Tsuna attacks Hibari and is beaten severely, however he steal's Hibari's box and attacks, which was his true intention. This is the second time during their fight that Hibari truly sees Tsuna as a worthy opponent. It appears that the enormous power Tsuna is capable of is still out of reach. However, Tsuna now fights with a much more powerful will and is becoming the boss Reborn has envisioned. Lal Mirch then proceeds to put him in an intense training regimine, to prepare him for all that he must do.
When an energy source is detected everyone thinks it could be interference or an enemy, however Tsuna knows that it's Chrome showing the development of his intuition and his bond to his family. He is worried for Chrome, who takes a turn for the worse shortly after being brought to the base. This only adds to Tsuna's stress as he contemplates the attack on the Millefiore's base in Japan that he and his family are meant to be part of in only five days time.

This stress has been shown to weigh greatly on Tsuna's shoulders and causes him to lash out and constantly question himself, even making him yell to Lambo and Haru after Lambo bothered Tsuna. This stress may be only another plot device, as it has in the past, to show Tsuna's true resolve and his worthiness as the tenth boss of the Vongola family.

• Dying Will Shot - When Tsuna is shot by Reborn's Dying Will Bullet, it uses the pressure he faces during a crisis to externally remove Tsuna's body limiters. He then uses his increased strength and renewed confidence to fulfill his dying will; the last thought he regretted before being shot.

Tsuna in Hyper Dying Will Mode wearing his X-Gloves.

• Rebuke Shot - When shot by the Rebuke Bullet, Tsuna is able to hear people's rebukes (criticism by others). It allows Tsuna's dormant 'Vongola Blood' to awaken. Rather than removing his body limiters externally, it awakens Tsuna's hidden willpower; internally removing his body limiters. He receives the same strength as he does with the Dying Will Bullet. It also removes the limiters on his internal senses giving him 'Hyper Intuition' (Tsuna already has a strong intuition, as does everyone who shares the Vongola bloodline). Although, unlike the Dying Will Bullet, the Rebuke Bullet allows Tsuna to apply his strength more calmly and wisely. He conserves energy and accurately expels it against others in a sharper manner.

• X-Gloves - Created by Reborn's pet, Leon, this gloves were made especially for Tsuna. He first used the gloves in chapter 78. At first, it appears to be a simple pair of white, wool mittens with the number 27 stitched onto it, but when used with the Dying Will Flame, it changes into a pair of black gloves with an X engraved onto it. It is made out of the same material as the Dying Will Bullets and can ignite the Dying Will Flame without the help of the Dying Will Bullet, increasing Tsuna's strength even more. It can also use the flame as a speed booster when the flames from the gloves are instantly released, causing him to thrust towards his desired direction.

Minus/Zero Point Break Through - Originally the Vongola 1st's technique. Tsuna goes into a state of Minus point, a pure negative of the dying will mode. In this state, Tsuna can extinguish, and possibly freeze, other's Dying Will Flame. His Dying Will Flame on his forehead along with his glove disappears, but the X-Glove doesn't change back to a mitten. Tsuna wearing his V. R. Version X-Gloves. Version Vongola Ring - First appeared in chapter 158 after the meeting with the previous Vongola Heads and breaking out of Kyoya Hibari's special box's ability, Spike Ball. The X logo on the gloves are now replaced by a material similar to the Vongola's Ring, but not much is known about its powers and uses yet, however they appear to have given Tsuna a huge boost in power. They also allow him to expell his flame from his hands in a concentrated manor in order to both attack an apponant or to propel himself. The gloves also seem to have a point where the power they give Tsuna jumps up exponentially, Tsuna has yet to control this.
Initially, when Tsuna awakened from his Hyper Dying Will Mode (X-Gloves in conjunction with the Dying Will Flame caused by the Rebuke Bullet), he was unable to move for two weeks without experiencing muscle pain. After strict training, he was able to compensate for his lack of strength and is now able to enter this mode without experiencing muscle pain afterwards.
Later in the series, Tsuna is able to enter into his Hyper Dying Will Mode using only the gloves and the pills that Basil gave him without the help of any bullet. Although it allows him to achieve his Hyper Dying Will Mode, this Hyper Mode is not as strong as the one achieved by the Rebuke Bullet.
In the future arc Tsuna purifies his flame with the help of his Ring of Sky and is able to freeze the flame which is emitted from other Vongola rings and the weapons combining them with a box produces. Apparently this was a unique power he had that made him renowned in the Mafia underworld before his death sometime before his past self arrived in the future.
Throughout the series, Tsuna seems have to some superhuman endurance even in his normal state. He has been able to walk away from being caught in explosions, beaten up by angry mobs, mauled by animals, etc. Most likely this is a joke since Tsuna is usually very unlucky.