During a solo trip, he meets Kiho, a quiet and beautiful married woman. The heat of the hot spring and the sense of freedom that comes with travel easily erase the boundaries between them. Their bodies, heated in the bath, press together, and without either of them knowing, their lips meet. It is precisely because of their casual relationship that they can freely express their instincts, enjoying the immoral pleasure. Her semen-filled moans cut through the silence of the inn, and the sound of flesh colliding on the tatami mat. He stains their one-time mistake with semen, imprinting an unforgettable, intense "hot spring mating" on his mind. A documentary of one night in which a married woman's hidden passion explodes.