He gladly lets Jean drop his weight onto him, having to fight back the urge to laugh into the kiss. He's used to that, Jean often does so after meals if he's tired, complaining that training has worn his muscles out and trying to get Bertholdt to give him a massage since Reiner says he's the best at it.

(It has yet to work, but hope springs eternal).

Jean pausing has Marco worried he's done something wrong, but then Jean opens his mouth and Marco realizes he's probably never kissed like this before. He shifts the hand on his neck to cup his head, helping Jean tilt his head a little as Marco slides his tongue into his mouth. He presses it against Jean's, trying to encourage him to move the organ against Marco's own.