This seasons 'Skip and Loafer' on Crunchyroll is excellent! It's not purely romance but that is a big part of it. It's high school aged characters but not written for a high school audience, the nuanced writing and excellent handling of various issues make it stand out as much more mature than many of it's counterparts.
Also from this season, Insomniacs After School on HiDive is very touching relationship growth between two realistic and likeable characters, though the animation and writing quality aren't quite as good as Skip and Loafer.
This is "are the straights okay" which is for exactly this kind of content.