'Mature' romance anime recommendations?

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:

Spice and Wolf

Science Fell in Love, So I Tried to Prove It

Wotakoi: Love is Hard for Otaku

Golden Time