Marin is making a big deal of confessing to Gojou but doesn't she already have what you'd expect of a couple? At this point in your relationship, where you're almost always together, eating under the same roof, comfortable(?) sleeping under the same roof, even comfortable with seeing/being seen half-naked, what's the point in "confessing"? Worst case it ruins what you already have, best case you continue on as always, maybe with an awkward phase in between the two normals.