it's funny that on a kuudere manga we don't know if he's jealous and wants to monopolize her just a little
or if he's horny
or if he fell in love
probably all at the same time
I got less of a "sad" vibe and more of a sense that he was distracted while trying to work through emotions he hasn't experienced before: jealousy, attraction, and the confusion or self-doubt that comes from them.