Ehm, where did the titties come from, are they like a part of the attire? Looks oddly natural in that frame.
I'm starting to question Nagisa's gender, it's not like he was confirmed to be a man either. Him being worried about the stalker despite being a guy and a cop on top of that doesn't add up to that behaviour.
But since the MC has been around him for a while now it's quite unlikely that he's not aware of at least suspects something.
Nagisa seems too feminine to be a guy. The way he thinks, the way he reacts, his knowledge of make up, his 「スタイル」, his way of dealing with that stalker problem, everything smells fishy, I just can't see him as a guy at all.
That is untill there's an obvious dick shown, which will never happen in this sort of manga, so yeah, a man can dream, I'd love this to be more than just my speculations.