Working as a part-timer, I live together with my older brother and his wife. My brother is busy at a trading company, often leaving early in the morning and returning late at night. As a result, I end up spending almost every day alone with my sister-in-law, Chika. She has a gentle appearance and treats me like a close friend. One day, I accidentally catch a close-up glimpse of Chika's private side. What I see is far removed from our everyday life, revealing a hidden allure I never knew she possessed.