Tsuna has really grow up... he dare even challenge Reborn... lets go back to why.
It is official, that the Arcobaleno Representative Battle took place in order to replace the current Arcobaleno by choosing the next strongest 7. According to Bermuda von Vichtenstein the pacifier behold by the current Arobaleno is dying and for the sake of world balance, Checker Face need to find another human sacrifices. hence, when the next 7 is chose the current Arcobaleno will basically die or (if their will or vengeance strong enough) turn into the Vindice.
Tsuna was determine to save Reborn and other Arcobaleno gather everyone, from his team to others'. His plan is to cooperate with them and to win for the sake of the Arcobaleno.His determination totally change him hence, receive the recognition from Xanxus, Hibari, and Mukuro as the Boss. Reborn however is against this idea. According to him "I won't send my student to a fight that I know he can't win." and ask for the Boss watch back from Tsuna. Disagree with Reborn, Tsuna challenge him to confiscated it from him as he won't surrender it by force or not. He even pick a word from Primo; "A man who are not willing to sacrifies himself for his comrades don't have what it takes to become the Boss of Vongola."
