amamiya ren and sakura futaba (persona and 1 more) drawn by enrique_bolatre

Okay, I didn't get this one at first, but Firestar4041 on the dub of this comic had an explanation for those who don't get it, so without further ado....

Firestar4041's Explanation

Joke is;
Joker is doing the "Had to do it to him" pose meme (just a pic of a guy standing on the street, with the caption "you know i had to do it to em")
Futaba being a internet gremlin, finds it hilarious