Mizuho (52) has been married for 19 years and has no children. She works part-time in an office, and her husband is five years older—an earnest, kind man she met through an arranged marriage. He has little interest in sex, but their relationship is stable and harmonious. Though they haven't had sex frequently over the past decade, she never felt dissatisfied. Three months ago, her husband suddenly made an unexpected proposal: "I've become interested in being cuckolded. Would you try it with someone else, just once?" Shocked yet intrigued by this unfamiliar side of him, she accepted, hoping it might bring a new change to their ordinary life. A new chapter has begun.