Ore no Oniku-chan

Ryuugasaki Kou is as fat as a meatball, and has a huge crush on his high school senpai, Hiiragi Chiaki, who calls him "Oniku-chan". On Chiaki's graduation day, Kou finally works up the courage to… not quite ask him out, but nevertheless he is horribly rejected! After working to lose all of his weight, Kou is now new and improved, but when he finally runs into Chiaki, he discovers that Chiaki is and always has been a chubby chaser?!