Kakashi Love Song Naruto: Shippûden : Season 9 Episode 16

A female spy, Hanare, from the Hidden Lock Village (Land of Key) is caught by ANBU pretending to be a musician. She is interrogated. However, the interrogation proves unsuccessful. Slowly, her past is revealed and so is her relationship with Kakashi. Team 7 spy on the two as they go around town, under the impression that the two are dating. After The Lock Village keeps a Leaf Village ninja hostage, they exchange Hanare for the ninja. It is then revealed that Hanare has a special ability, causing a large chase to occur. In the end, Kakashi lets Hanare free. The musician seen at the beginning entertaining Konoha ninja reminds Kakashi of Hanare which prompts the flashback.