This feels like the title screen to a cutesy sports game with very bright colors. It could also be a Paper Mario (for N64) level, as it has a certain whimsical quality to it. I like this a lot. I have a couple of things to note:
1: I'm not entirely sure about why the title of the song is called rainsets. To me it sounds like a sunny day in a green grass field; the title rainsets doesn't really make sense IMO.
2: More of a positive thing, I love that you said the genre of the song is Synthwave. Synthwave has been around long enough to have tropes associated with it, none of which you used. I'd argue that's a good thing, since sometimes Synthwave can have a certain stylistic repetition to it. This song seems like a breath of fresh air.
Nice work! :)