The Battle of the Sky, Begins! (大空戦, 始まる!) is the 57th episode of the Katekyō Hitman Reborn! anime series.
Everyone arrives at Nami Middle to find Tsuna and Xanxus about to fight. The Cervello put watches on the Guardians that poison them and the only antidote is to put their Vongola Ring in the watch itself. Just before the fight begins Xanxus makes a decisive first strike.