SakuKarin

SakuKarin is a Femslash ship between Karin and Sakura Haruno in the Naruto series.

Canon
Sakura and Karin first met each other during the mission to pursue Itachi but the two did not acknowledge each other. They did not formally meet until Five Kage Summit. Sakura was ordered by Sasuke to kill her if she wanted to join him to which she hesitated. However, it turned out that this was a ruse for Sasuke to sneak up on her so Kakashi saved her and ordered her to heal Karin instead of killing her.

While Sakura was healing Karin in a safe area, she felt pity and sympathy for her because Sasuke was willing to have both of them killed. Karin did not want pity and begged Sakura to stop crying because she was an enemy and thus should not be sympathizing with her. Sakura later introduced her to Naruto as a member of Sasuke's team but she denied this.

Years later, Sasuke was away from Konoha on a mission with Karin and Sakura followed him during the process. Sakura eventually married Sasuke and was pregnant with his daughter. When she went into labor, Karin was the one to deliver her baby. She also provided her with glasses as she had poor eyesight. Karin had also loved Sasuke but wanted him to be happy and was willing to help him and Sakura because of this.

Fanon
SakuKarin has a decent amount of popularity in the Naruto fandom. Sakura and Karin were often considered to be rivals due to their love for Sasuke and the fact that they were technically enemies for a while. Some fans decided to ship them together because of or despite this because they felt that they would go well together. There is also the fact that both are medical ninja. SakuKarin rival SasuSaku, SasuKarin, and other pairings involving Sakura or Karin.

Trivia

 * Karin was immediately able to notice Sakura's feelings for Sasuke.