Kakashi & Itachi Anbu

When Minato was elected Hokage sometime later, feeling that Kakashi needed a new direction in life following the loss of Rin, he assigned Kakashi to join the Anbu despite his student's young age under his direct command.Three years later, Itachi Uchiha, another prodigy even younger than Kakashi was at the the time, joined Anbu as part of Kakashi's team. While Kakashi's men doubted letting such a young child join, Kakashi noted Itachi's exceptional capabilities. Later, Kakashi and Itachi were assigned to a mission of observing a meeting between Konoha and the Land of Woods. They were tasked to kill the Land of Woods' Prajñā Group if they betrayed the Konoha-nin after an exchange of scrolls was made. When the Wood-nin revealed their treachery, Kakashi and Itachi swiftly defeated them. Afterwards, Kakashi congratulated Itachi for his excellent performance. Also watching Itachi's merciless approach made Kakashi realise the dark side of being in Anbu, telling the young Uchiha the importance of friends.