Shitsuren Chocolatier

From Aerandria Scans:
Souta, who's attending a confectionary school, is in a relationship with Saeko, a girl one year older than him. He fell in love at first sight with her four years ago, and right before Christmas last year, they finally had their first kiss. Because his girlfriend really loves chocolate, every day, Souta tries to polish his chocolate-making skills. Even when his girlfriend smells like cigarettes although she doesn't smoke, even when she turns down his invitation to a date on Valentine's day, he's still not broken-hearted at all, and he still continues to love her.

Note: Won the 2012 Kodansha Manga Awards in the Shoujo category and was nominated for the 4th Manga Taisho Awards in 2011.