A group of female guests staying at a hot spring inn. While enjoying the inn's famous open-air bath, something strange happens to their bodies... They feel short of breath, their chests get hot, and an indescribable pleasure runs through their entire bodies from deep within... The powerful aphrodisiac that the innkeeper secretly mixed into the bathtub takes effect on the women, and they are unable to resist the excitement that has been set in them, as they are toyed with by the men in the open-air bath.