Side Story 1: Mission Start…!! (外伝其ノ一:任務開始…!!, Gaiden Sono Ichi: Misshon Sutāto…!!) is chapter 239 of the Naruto manga.
It is the time of the Third Shinobi World War. Obito Uchiha is running late, for which his team-mate, a young Kakashi Hatake, reprimands him when he eventually arrives. Kakashi, having recently become a jōnin, is given gifts by his team-mates. Rin Nohara gives him a personalised medical-kit. Their master, the future Fourth Hokage, gives him a special kunai. Obito has forgotten to get him anything. Kakashi is to be the team leader for their mission to destroy the Kannabi Bridge, which will give Konoha an advantage over Iwagakure in the war effort. As they travel through Kusagakure they discover they are being watched by an enemy ninja. Kakashi decides to deal with the ninja with a new technique: the Chidori.