The Truth of the Mist is the 52nd episode of the Katekyo Hitman Reborn! anime.
The unexpected person, turned from Chrome Dokuro, to Mukuro Rokudo. A series of chaotic illusions battle starts. During the fight, Tsuna experiences flashbacks of Mukuro on how he sacrificed himself for Ken Joshima and Chikusa Kakimoto to escape. Mukuro ends up being the winner, almost killing Mammon, but they escape from the battle field with their reserved power. Mukuro faints after the battle, turning himself back to Chrome.