Dreaming of a happy family with his fiancée, Hee-kyung, Lee Yoon-woo moves to a quiet, rural village where he has no connections. But one day, Hee-kyung leaves home, leaving only a short text message saying goodbye. Abandoned by his fiancée and struggling to adjust to his new school, Yoon-woo is struggling when her younger sister, Chae Jeong-min, his first student and a friend from their college days, shows up... "Hello, teacher. It's been a while." "Oh, not teacher... Should I have called you brother-in-law?" Despite Yoon-woo's protests , Jeong-min invades his precious home, which he hadn't even cleaned, fearing any trace of Hee-kyung would disappear. He then rummages around, proposing to live together... "I have no one to turn to, so I'm just chasing after my ex-girlfriend who ran away." Yoon-woo and Jeong-min cannot refuse, but will their cohabitation be ok?