So I’m looking for a somewhat-mature to mature romance. I want the main couple to go past just kissing, and I don’t want that to just be implied. I want the romance to actually build though. Besides that, please no harems. Also, I really hate male characters who are rude and mean to the females and vica versa. Some examples of manga I have read that fit these requirements are Devil’s Line, Namaikizakari, and Kiss Him, Not Me.

Bonnouji
Kimi wa Pet
Sekine-kun no Koi

And maybe Taisho Wotome Otogibanashi - It goes further than kissing but I wouldn't really describe the relationship as "mature" since the characters are a bit unrealistic. But it's cute and idealistic.

Ai Hime - Ai to Himegoto is a pretty good one IMO