In the fifth year of their marriage, husband Satoshi remained consistently serious and sincere in everything he did. His wife, Saeori, had originally been drawn to this earnest nature, and their relationship had been harmonious. However, as time passed, she gradually began to feel that his seriousness was turning into monotony. In this household, Satoshi had an irresponsible younger brother who held no steady job. When he secretly spies on Saeori during an intimate private moment, the shock of this incident sets the story into motion.