About Vongola Primo and the Shimon Boss Cozart

The Sin:

Vongola`s heirloom In the succession arc, as Tsunayoshi accepted the inheritance as the 10th boss because his friend and guardian Yamamoto, was beated by an unknown people. In the ceremony, another mafia family called Shimon shows up and stole the "Sin", which is the Vongola`s family heirloom. The legends say that the "SIN" is created by Vongola Primo - Giotto to leave the memories of his battles to all his successors as the proof of the Vongola Boss. It is also said that the bottle contains the blood that was shed in the battle. The SIN is kept through the Vongola generations, however, no one truly knows what the SIN is till the Shimon family took it in Tsuna`s inheritance ceremony. The Shimon family is said to be one of the families that helped the Vongola family in the first generation, but left the country and disappeared. These is the side that the Vongola family knows, however, Enma Shimon the current boss of the Shimon family proclaims that the SIN is the blood of their first boss which Vongola Primo betrayed.

I don`t deny that the blood of the Vongola runs through me.. neither do I have the ability to find out what really happened between Vongola and Shimon. But there is one thing I can swear on my grave. VONGOLA PRIMO IS A MAN WHO WOULD NEVER DO SUCH A THING!! - Tsuna | Chapter 297
The Legend:

Vongola Primo and Cozart The Shimon family states that Vongola Primo betrayed the Shimon family by using the Shimon family as bait. The Shimon family fought along side the Vongola family and were in deep friendship. However, as the Vongola claims the power across Europe, Vongola tricked the Shimon family by using them to lure the enemy with 20 thousand men while the Shimon family agreed and brought only 50. The Shimon first boss, Cozart died while waiting for the help of the Vongola family which never came. The members of the Shimon family died miserably while the survivors were left to perish. The Vongola family put the blame on the remaining Shimon family and left them to suffer and looked down upon. By then the Shimon family were treated as criminals and hid themselves. On the other hand, the Vindice, the Mafia group of reapers, stated that Vongola Primo and Cozart Shimon had unfettering friendship and a promise. A promise that the Vongola family and Shimon family are bound not to cross swords with each other. And if they do, the loser will be erased from existence forever. It was also said that the fight between Tsuna and Enma is the second time to be put up. The losing participant will remain in Vindice prison forever.

On the other hand, in Chapter 313, it was shown that it was Cozart`s idea that made Giotto make a family to protect the weak people which Giotto called Vongola. So is it the truth? Vongola Primo betrayed Cozart? As Tsuna have said, Vongola Primo is a man who would never do such a thing, but what did happen? We don`t know yet, but if you think about it as the Vindice said that the fight between Tsuna and Enma is the second time Vongola and Shimon crossed swords with each other. So who where the first one? It might be Vongola Primo and Cozart, since it was also said that the loser will be erased forever and stayed as prisoners. There might be a fact that Cozart lost his battle against Giotto which sums up the current status of the Shimon family, they are treated as criminals. Maybe Enma`s (the current Shimon boss) ancestors, the early Shimon generation, were in prison for a long time. This are just my theories, but there is also a possibility that Daemon, Giotto`s Mist Guardian who hates Giotto`s ideals, was the reason why Cozart and Giotto fought each other. Another thing, the blood of Vongola Primo which is kept to be used to upgrade the 10th generation Vongola rings was called "Penalty". Does the name for both treasured blood symbolizes the truth between Giotto and Cozart. If Cozart`s blood is called "SIN" which would mean that he committed a sin against Giotto while Giotto`s blood is called Penalty which would mean Giotto suffered; there might be a connection but this is just my speculation. We still don`t know the facts, and the story is not broaden yet. Let`s just wait till the truth about Cozart and Giotto is finally released.