Fateful Showdown is the 170th episode of the Katekyo Hitman Reborn! anime.
After Tsunayoshi Sawada defeats Torikabuto with the help of Nuts, Takeshi Yamamoto encounters Saru. Saru reveals himself to be none other than Genkishi. However, Yamamoto surprises Genkishi with Koziro, his Box Weapon, merging with Shigure Kintoki to form Ugetsu Asari. His other Box Weapon, Cane di Pioggia ver. Vongola, changes his three small swords as well.