reading 18+ at the very top of the page kind of put it in my head too that it would have NSFW content, (Edit) plus the gay tag implies romance, like you said in a previous comment, but then you say there will be no romance in this comment despite that other one
i feel like if in this situation, 18+ means stuff like blood, gore, other such 'mature' content then I think 16 (Edit) or 17+ would fit better
that's just my brain tho haha love the work !