The Unexpected is the 214th chapter of Akira Amano's Katekyō Hitman Reborn!
Synopsis
Tsuna attempts to fire the X-Burner, but fails, as Genkishi lands a hit on Tsuna while he's preparing. Reborn states that the time gap needed to fire the X-Burner was too large, so it would be ineffective on Genkishi. Genkishi attacks with an illusion that multiplies his swords. However, Tsuna quickly dodges and propels himself with his Dying Will Flames. Genkishi chases after him and slashes his swords. However, that Tsuna is revealed to be a hologram, and Tsuna shoots the X-Burner at a low temperature. Because of the low temperature, Genkishi plunges his sword through the hard flames to Tsuna, but Tsuna retaliates with his Zero Point Breakthrough: Revised.
Characters
Note: Bold + Italicized = First Appearance