Sumire, a brash young mother who has just moved upstairs, stops by to introduce herself. Days later, flashy underwear lands on the narrator's balcony, so he takes it back to her—only to find her waiting in an outrageously revealing lingerie set. She admits she noticed him checking her out and pounces at the door. From then on, every pair she drops becomes an invitation to another sweaty fuck while her son is away.