f(x)'s Amber showed her love for her SM Entertainment hoobae and new Red Velvet member Yeri.

Amber, who's known to be a social butterfly in the K-pop world, posted the above photos to Instagram on March 24 as well as the message, "Yeri, you're having fun after your debut, aren't you? Congratulations! When I see you, the only thing I can think is how old I am. I care about my Yeri."

The f(x) member wasn't afraid to show her affection for the youngest member of Red Velvet, who recently debuted with the group's "Ice Cream Cake" album.

Fans responded, "I can't believe they're 7 years apart," "I care about f(x) and Red Velvet," and "It makes me feel warm and fuzzy seeing the sunbae-hoobae love."

Did you know the two were friends?