Babo (2008)

Ji-ho is a promising pianist, studying and playing abroad for years, but one night she has stage fright and never recovers. In despair she comes home and meets her old classmate Sung-ryong. Once a very bright boy, Sung-ryong had an accident and now he is in late 20s with the mind of a six year old. He is very forgetful, but he has never forgotten his first love Ji-ho. Sung-ryong has a younger sister named Jee-in. To take care of her, he sells toasts in front of Jee-in's school, which embarrasses her so she ignores him. Sang-soo is Sung-ryong's old friend, who understands Sung-ryong's innocent mind, but he inevitably falls into the criminal underworld of gangsters. Ji-ho is still in her slump, Jee-in falls sick and Sang-soo gets involved in a bloody dispute--but all of their agonies are miraculously saved by Sung-ryong in a way no one expects.