It's from Naruto Shippuuden Episode 431: To See That Smile, Just One More Time.
This one is from the run of Infinite Tsukuyomi fillers that aired during the Fourth Shinobi World War arc. Notably, unlike the previous episodes in this set of fillers (mainly just fairly lighthearted happenings inside the Infinite Tsukuyomi dream of various characters), Karin's episode here is basically a rather sombre flashback to her past.
(This was a sad episode. Poor Karin...)