Hmm~ Well, he'd try. xP Well, not so much to piss him off, but he'd be weird anyway just to see his reactions- and if anger is one of them, so be it.
Ivan is definitely Bi or Pan, not entirely sure which one, so it's not like he'd be entirely freaked if a guy say, took interest due to his flirting- but he would be freaked over anyone taking interest in him period. Especially if Unseen flirted back. That would turn the tables super fast. Not that I'd expect him to, but just saying. xP
That said, we could just see what happens, might be funny. Not entirely sure how they'll meet, though.. They are the same age, but Ivan's a highschool student. So we'd need to find an area outside of school for them to meet. Maybe during one of Ivan's public antics? Or maybe he just catches Unseen doing.. something that catches his interest.