Meeting Cozzato & Creation of Vongola Edit
Prior to founding the Vongola, Giotto and G met the first Simon Famiglia Boss, Simon Cozzato when Giotto returned his wallet that he purposely dropped with intentions of helping their poor neighbor, Paolo. When both realized they had done the same thing, they introduced themselves and started becoming friends since then. One day, one of their friends, Franco, was attacked by some thugs after he refused to give 90% discount and the doctors were threatened to not help him. Sickened by this incident, Cozzato suggested to create a vigilante group with Giotto as the leader in order to protect the town and its people from the outlaws, and thus, creating Vongola Famiglia; however, not as a part of Mafia Famiglia the way they are now, but as an independent group to protect people. It was presumed that during these times, Giotto received set of seven Vongola Rings from the first Giglio Nero Boss, Sepira.
At some point during his reign as the Vongola Primo, he feared that the Vongola would start to fight for self-interest and decided to disband his military forces, which caused Vongola's territory to be open to an attack. As a result, a duke's daughter and one of their members, Elena, was killed. This event led Giotto to be betrayed by his own Mist Guardian, Demon Spade, who wanted the Vongola to be more than they were at that point in order to fulfil his promise to Elena, his lover at the time.
The Oath Between Vongola and Simon Edit
During a huge war with a rival Famiglia, Knuckle informed that Cozzato and his Famiglia are cornered within the enemy's territory and was about to save them, but stopped by Demon who volunteered to help them instead. Giotto, realizing Demon Spade's true plan, ordered G and the rest of his Guardians to secretly save Cozzato and his Famiglia. Afterwards, he, Cozzato, and G met up and discussed what they should do with Demon. Cozzato suggested to keep their survival a secret and then he and his Famiglia would go into hiding, disappear from the world's eyes. Giotto was upset by Cozzato's suggestion and immediately rejected the idea, not wanting them to carry the burden of his Famiglia. However, realizing Cozzato wouldn't back down, Giotto finally agreed under condition that the Simon would always help Vongola as long as the Famiglia exists. Hearing the vow, Bermuda von Veckenschtein and Jaeger appeared in front of them and declared they will imprison those who lose the battles if Vongola and Simon ever crossed swords against each other. Giotto and Cozzato agreed on the condition that after each battle, they must show their successors their true history. After this, Giotto and Cozzato never met again for the rest of their lifetimes, but believed that one day their true descendants who are bearing their wills will meet each other and smile together like them once again.
Demon Spade's Betrayal & Retirement Edit
Sometime afterwards, Demon finally directly betrayed him, deeming him unworthy to become a Boss of the current Vongola since the Famiglia Giotto had created had become stronger than he could have ever imagined, stating that he merely accelerated the process. After the betrayal, Giotto sealed the true power of the Original Vongola Rings, as he didn't trust what the Vongola would become. Also wanting to distribute his power in order to restrict the selection of the next Vongola later on, he sealed the highest output of the Rings' flame energies so it could be split into two; one for the Vongola Boss, and for the External Advisor, creating CEDEF with Alaudi as the founder and leader, while choosing Vongola Secondo as the next boss. Once Vongola Secondo was appointed, Giotto officially retired and moved to Japan, starting his own family which began with his son Yoshimune. Through Yoshimune, the Japanese part of his bloodline has extended with Yoshinobu, Ietsuna, Iemitsu and finally Tsunayoshi.
During Tsuna's training with Hibari, he was trapped, enclosed by Hibari's Cloud Hedgehog, and forced Tsuna to undergo the Vongola Trial of Succession. While Tsuna was trapped in the hedgehog, his Vongola Ring emitted images to his head. The previous Vongola Bosses stated that they were the past sins and crimes of the Vongola. The bosses demanded Tsuna to accept the bloody history of the Vongola if he wanted to be strong, but Tsuna refused to do so and stated that he would rather destroy the Vongola than accept their sins. Vongola Primo then accepts Tsuna as the successor to the Vongola and grants him the proof of the Vongola.
He appeared through Tsuna's Vongola Ring and Arcobaleno Pacifier, answering Uni's will. He stated that he never answered to the Arcobaleno's power and never will again, but is making a single exception due to Uni's condition; it is never revealed what Uni promised him. He told Tsuna and the others they have yet to inherit the Vongola's true power and that the First Vongola Guardians will observe them to see if they are worthy to inherit Vongola's true power or not. Before he disappeared, he asked if they were able to embody the duty of a Guardian and if they had that resolve because everything rested on that.
Lightning Guardian Succession Trial Edit
Later, he appeared at a castle inside an amusement park where Lampow decides that he will stay until his Succession Trial finishes. Giotto said that it was his turn now. At first, Lampow was against doing this, but Giotto was able to convince him as Lampow also commented that he "can't say no to him."
Storm Guardian Succession Trial Edit
During Gokudera's Succession Trial, he sealed Tsuna's Hyper Intuition to prevent him from finding out G's identity who was disguising as Gokudera, but later realized it was pointless to seal it because Tsuna could still felt that G wasn't the Gokudera that he knows. After G's trial, he said that Tsuna realized that G wasn't his real Storm Guardian even though he already sealed his Hyper Intuition and thanks G for his help when they remembered the times when they first built the Vongola, something that both he and G never regretted.
Mist Guardian Succession Trial & Vongola Decimo Succesion Trial Edit
He appears again at the Namimori Shrine along with his Guardians, looking a bit worried as the next trial would be Demon Spade's one. He checked his pocket watch before standing up. He again along with the other Guardians watch Demon Spade's trial from afar. The other guardians wanted to intervene, but Giotto just told them to wait and watch, stating that this will be the perfect time for them to determine the true mettle of Tenth Generation Vongola Family. A few moments after the start of the trial, G once again questioned was it really all right to let Demon do as he pleases. Giotto remembered the time when Demon betrayed him and despite being told by G and Knuckle that what happened before wasn't his fault since Demon had already chosen different path from the start, Giotto states that the fact Demon is his Guardian doesn't change, wondering that Demon Spade's time may have stopped at that time like their pocket watches does.
Once Demon decided to give his inheritance, Giotto appears again in front of Demon and thanks him for fulfilling his duty as a Guardian to which Demon commented that he hasn't changed. After Demon gave Chrome his inheritance, Giotto also gave Tsuna his inheritance as he had watched Tsuna and his Guardians throughout the Inheritance and impressed by their determination, deeming him and his Family worthy to carry out the legacy of Vongola. Later, he approaches Demon and comments that Demon still keeps the pocket watch that symbolizes their friendship and said that his feeling regarding that matter has yet to change, to which Demon replied that he was forever a fool and that's why Giotto disappointed him in the end. After both parted ways, he and the other Guardians went back inside the Vongola Rings.
When Tsuna had his back to the wall in his battle with Byakuran, Tsuna explained his motives for fighting and prepared to battle Byakuran again, although he was heavily out classed by Byakuran, something Byakuran was quick to point out. At this moment, responding to Tsuna's will, Giotto speaks, but doesn't show himself, through the Vongola Ring. Giotto speaks to his Guardians, asking them if they approved of what he was about to do. Each of his guardians approved, for exception of Demon, with G telling him to do what he wants, like he always does. Giotto agrees with G, and then appears in front of Tsuna through his Sky Vongola Ring. Giotto explains to Tsuna about the history of the Vongola Rings, and how their true powers were sealed to ensure a strict succession. However, now he believed that Tsuna would understand the true meaning of both the Vongola Rings and his will, so there's no need to seal them anymore. Upon saying this, Giotto releases seal on the Vongola Rings and reveal its true form. After doing this he encourages Tsuna to beat Byakuran by telling him to give the "Mare Boy" a scare before disappearing.
When Talbot, the oldest metal craftsman who worked for Vongola, arrived, after the Vongola Rings had been heavily damaged due to the Simon's attack, he revealed that he could repair and upgrade the Vongola Rings with a bottle called Penalty which contained Primo's blood.
These Keys were objects that were used by Cozzato and Giotto, and given to the Vindice to be presented to the descendants of Vongola and Simon when the inevitable battle between them commenced. These keys held the memories of the two bosses, and would reveal the true history behind the two Famiglias.