Following their father's job transfer to Sapporo, Yuuto and his stepsister Erika settle into an empty home and gradually explore a closer, more intimate connection. With no one else around, their daily interactions shift into uncharted territory as they navigate these new feelings together. At the same time, Yuuto's art teacher Sayaka Ichinose detects the subtle changes in his attitude and finds herself increasingly intrigued by what might be unfolding.