KakaSasu

KakaSasu is a Slash ship between Kakashi Hatake and Sasuke Uchiha in the Naruto series.

Canon
Sasuke is one of three students who was placed on Kakashi's team. He initially struggled to pass his test but managed to do so when he offered to feed Naruto despite the fact that it was against the rules. Kakashi admired Sasuke from the start because he reminded him of himself and his friend Obito. Between the second and third rounds of the Chunin Exam, Kakashi decided to train him over Naruto and taught him the Chidori.

When Sasuke grew jealous of Naruto and fought him on the roof of a hospital, Kakashi tied him up and lectured him. He warned him that getting revenge against Itachi would not make him happy and that he needed to get over his sense of superiority. Kakashi also reminded Sasuke that Chidori should not be used against his friends. Sasuke responded by saying that Kakashi did not understand how he felt until he reminded him that all of his friends are already dead.

Sasuke eventually decided to leave the village in order to go train with Orochimaru. Over two years later, Kakashi attempted a mission to capture Itachi in order to lure him but it failed. They were finally reunited in a battle during the Five Kage Summit. Sasuke had no respect for Kakashi by this point. Kakashi attempted to finish him off but Naruto intervened so he decided to trust him.

During the Fourth Shinobi World War, Sasuke finally came to his senses and decided to fight for the village. He and Kakashi later fought side-by-side as a part of the reformed Team 7. Kakashi began to have hopes in Sasuke because of his Rinnegan. He was disappointed when he decided to battle Naruto again and prevented Sakura from intervening. When the battle ended, he was happy to see Team 7 get along once more.

Fanon
KakaSasu has a decent amount of popularity in the Naruto fandom. It is not as popular as other ships such as SasuNaru but it still has its fans. Many fans ship it due to their bond as mentor and student and the fact that Kakashi sees a lot of himself in Sasuke. There is also the fact that he decided picked him over Naruto when deciding whom to train before the Chunin Exams. KakaSasu tends to rival the SasuNaru and KakaNaru ships.

Trivia

 * Sasuke is often portrayed as being similar to Kakashi when he was his age.