I don't want to be harsh on this, cause I'm very happy to have a Love Live Sunshine spinoff at all, but I feel like Sunshine in the Mirror could've been a lot better than it was. Specifically it seems pretty halfhearted in a lot of what people want from something like this. It doesn't get rid of singing and performances, but there's less singing than one would expect from Love Live. It's set in a fantasy world, but with plenty of modern amenities (and some tokusatsu elements?) and it never leaves the single town of Numazu. It has everyone from Aqours, but other thanthe eponymous Yohane, Lailaps gets more focus than all of them combined. And as far as I remember from Love Live Sunshine, Lailaps is a completely new character for this, and one I don't find all that likeable. As for the Aqours members themselves, their personalities only vaguely resemble how we know them, if at all. Mari's case is especially egregious, with the loveable, bubbly troublemaker becoming a secluded, depressed demon lord.
All that said, while the lack of adventure and relation to Love Live proper I expected is disappointing, I still think Sunshine in the Mirror is a good anime and a good addition to the Love Live series. Visually, it's beautiful, with intricate lighting, beautiful colors, and great attention to detail. All the Aqours girls, despite their differences, are still loveable, especially Yohane. What songs the girls do sing are very good. I would very much appreciate more content like this from studio Sunrise.