Living alone, hero unexpectedly meets married woman Yuki at a coin laundry during his daily routine, leading to an unforeseen turn of events. When Yuki visits due to a washing machine malfunction, she accidentally drops her underwear on her way out, and hero impulsively takes it home. Several days later, they meet again at the same laundry, and amid awkward tension, Yuki drops her underwear once more—prompting hero to take it again on impulse. That night, Yuki suddenly shows up at his place, pushing the story into a bold new direction.