Quick recap
A flashback to the Third Great Ninja War. Kakashi, freshly promoted to jōnin, leads Obito Uchiha and Rin on a mission to destroy Kannabi Bridge while their teacher Minato fights on another front. Kakashi is cold and lives by the rules. When Stone ninja abduct Rin, he wants to stick to the mission, and Obito goes after her alone. Kakashi comes back, loses his left eye protecting Obito, and Obito awakens his Sharingan. During the escape, a boulder crushes half of Obito's body. With no way out, he gives Kakashi his Sharingan as a promotion gift. Minato arrives in time to save Kakashi and Rin. Kakashi carries his friend's lesson from then on.