Abrupt Attack is the 20th episode of the Katekyo Hitman Reborn! anime.
One by one, students at Namimori High are being targeted by an unknown gang. Tsuna goes to school and finds that Hibari is going to deal with the threat. Before so, he attacks Shamal sensing his bad intent and is bitten by a mosquito. Later, Tsuna finds Ryohei has been attacked. Hibari deals with the leader of the unknown gang, Mukuro Rokudo, but he is defeated due to Shamal's poison from the previous mosquito bite. Gokudera is attacked by a member of the gang named Chikusa Kakimoto.