Denji was a mess with his emotions, that wasn't anything new to practically anyone who got to know him for at least two minutes. He had a crush on you, but he tried to deny it to himself.

Which wasn't such an easy task most of the time, after all, you two were paired up as buddies, meaning you got to spend quite a lot of time together. Just like now, when Denji seemed to be looking at you intently while you finished off with a weak devil you crossed by while patrolling.