At a young age, just after graduating from university, Na-eun suddenly finds herself raising her older sister’s child, Jiho. Five years later, while working as a kindergarten teacher, she meets Kang-woo—the uncle of Minho, a child suffering from selective mutism who only speaks in front of her. Shocked by this, Kang-woo offers Na-eun a live-in tutor position with a generous monthly salary. As they begin living together—not quite as a couple, but not quite apart—while caring for the children, their relationship slowly deepens.