Looking for some romances that aren't so childish. I'm okay with a high-school setting if the characters don't feel like infantile, for example Sakurasou vs Your Lie In April.
To start, some I enjoyed are:
Science Fell in Love, So I Tried to Prove It
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.
skip and loafer JUST ended airing so im looking forward to watching that. i'll also try insomniacs after school after, but skip and loafer is definitely coming first :p