Not really cause in the end ilic realizes that he's gone "mad" cause when the guy asked him what's his type he just described him, so I think it's kind of clear that they like each other so it's not much of an open ending, especially as they've been together for like a decade now (●'◡'●)ﾉ
for me it's an open ending, but yeah they're very much "in love" even tho illic didn't really confess his love for sayan but anyways i think the novel has special chaps. idk if they'll turn it into a manhwa and add it here or leave it as it (i really hope the former ;-;)
i cried out of frustration because unfortunately, this is open ending. the ending depends on you. whether they really loved each other, they went their separate ways after this, they died, or whatever. god how i hate open endings :(