U don't know me Américaine (Net Comics)

Seyun, a lithe and catty high-schooler with a mysterious past, and Yoojin, a rough-and-tumble, straight-laced Judo star, have known each other since they were children. Growing up in the same place, they're bound to have differences, and when a tragedy befalls Seyun's family, he's forced to give up his home and move away from Yoojin. A new school, new friends, and years later, Yoojin and Seyun find themselves walking vastly different paths, while struggling to maintain their friendship. But when old feelings start resurfacing, a bitter tug-of-war starts, with hearts in the balance, secrets in the closet, and twists that nobody sees coming!

U Don't Know Me series was originally published as donginji (doujinshi) in Korea.
Chapter 1 thru 6 collects the three donginji books published.