On a certain day at the age of 17, Han Ye-ra visits a villa in another city to meet her mother's friend. There, she meets for the first time her mother's friend's daughter, Lim Se-yeon.\n\n"I saw everything. I saw what you did earlier, unnie."\n"What did you see? What did you see?"\n"You touched my thing, didn’t you? I saw everything earlier."\n\nYe-ra is taken aback by the bold provocation of the little girl, who cannot simply be dismissed as a child, and she has to leave the villa in a hurry without even having the chance to explain herself. This is because Se-yeon's mother suddenly ran out of the villa and got into a traffic accident. Thus, leaving behind the mysterious death incident, Ye-ra completely erased the events of that day from her memory.\n\nYears later, while teaching children as an English instructor at an academy, Ye-ra encounters Hyun-woo, her mother's old friend. At the request of her mother, who is going to a professor position in the U.S., and Hyun-woo, Ye-ra begins an unexpected cohabitation with Hyun-woo's daughter.\n\nThe girl is charming yet somehow sharp, innocent yet cheeky, leaving Ye-ra at a loss for what to do, and she begins to feel a strange anxiety from the gazes surrounding her. Then she discovers another shocking fact.\n\n"Unnie, do you remember? We did this together before."\n"What are you talking about?"\n"I remember. Why don’t you remember?"\n"Could it be you? That kid from back then?"\n\nThe daughter of Hyun-woo and the daughter of her mother’s friend who died in a traffic accident. Moreover, this girl is an ignorant homophobe?\nCan this dangerous cohabitation really end safely?