After a long time without seeing each other, a group of four close friends went to soak in a hot spring. The purpose of this trip was to have an affair; a couple who were already married secretly engaged with each other, and this was the best opportunity for them to be together. To keep it from those around them, after getting drunk, they sought each other out in the bathroom and had relations throughout that night. Later, this girlfriend became pregnant and it is very possible that her husband is not the father.