Well, it's manga with dense MC, but I kinda wonder now, if there actually exists at least one 16-17 y.o. boy who head over heels for some girl who's openly flirting with him, lovey-dovey with her to the point when they act like proper couple, receiving erotic pix from her etc and who's looking at her lips with flustered face and and thinking: "Hm... we are just friends, right? Hm... wait, i want to kiss her? Nooo, it's not like this of course".
I can even understand his doubts about her feelings despite all her attention to him, but it's almost impossible not to realize when you are romantically\sexually attracted to girl, especially when you are pretty much already in relationship. It looks dumb even for romcom.