Similar: Kimi ni Todoke, Suki-tte Ii Na Yo.
Complete - Mid-length: 51 chapters
As you can see by the picture, the mangaka is amazing. The actual manga itself isn't this detailed but it's still wonderful:
Basically, it follows a group of friends that have ended up together because they are all different: Mizutani Shizuku (booksmart and loves studying because she wants to be as accomplished as her mother, no idea how people work), Yoshida Haru (violent and has no idea how society works), Asako Natsume (gorgeous but draws in unnecessary attention from guys and is hated by girls, likes to live online), and Sōhei Sasahara (loves being loved by everyone but doesn't often reveal his inner thoughts).
It's super slice of life so there isn't a plot. It's just follows the lives of the main characters and how they interact to one another. A decent amount of main characters are slowly added as the story goes on.
One of the strong points of this manga is the realistic feel. None of the characters have the same feel; they are all themselves trying to deal with everything going on around them. And it's even more impressive as the amount of characters go up.
The artwork always gets better and the characters get more and more lovable as the story progresses.