Looking for a shonen or seinen manga where the main character falls in love with a really pretty girl, tries to make her love him and improves himself. But as time passes he meets another girl which he likes and starts a relationship with her. The other beautiful girl realizes her loss and tries to get him back because she realized she loved him.

I know, I was dumped a while ago so this makes me feel better.

Exactly what happens in Aku no Hana. Though it's very heavy so if you don't like the psychological genre, I recommend that you shouldn't read it.