After unexpectedly becoming the non-biological mother of her nephew Ji-Ho at a young age, Na-Eun builds a quiet life as a kindergarten teacher. But everything changes when Gang-u, the uncle of Minho, a child with selective mutism, offers her a high-paying live-in tutor job after discovering the boy only speaks around her. As they care for the children together, their unusual living arrangement slowly grows into something more than co-parenting.