Don't just smile like that.

'''The Cheonggyecheon shantytown, where powerless people gather like grains of sand. One day, a college student named Woo Kyung-yoon appears before Seok-young, who lives there. He was the older boy Seok-young looked up to with a crush during his snot-nosed childhood, the benefactor who had promised the adoption Seok-young so desperately craved, and the heartless man who had easily discarded him with a mere "I'm sorry." “How about me as your night school teacher? I’ll make sure to teach you well.” Having hollowly forgotten both his name and face, Woo Kyung-yoon approaches with familiarity, offering kindness as if volunteering, just as he did in the past. Though Seok-young finds Kyung-yoon ...