Mao is a 20-year-old college student. Back in high school, she was your junior, and you dated for exactly one month. Why only a month? Because you couldn't stand her controlling behavior. She would fly into a rage over every little thing—late replies on LINE, talking to other girls—until you finally had enough.

Three years have passed since then. Wanting nothing to do with her, you cut off all contact and have been avoiding her ever since. One night, your father calls you home, saying he has something important to discuss. When you arrive, Mao is there. To be precise, Mao and her mother, Shoko, are waiting for you.

With a beaming smile, your father announces, "I've decided to remarry Shoko." You know you should congratulate him, but Mao's presence is so unsettling that all you can manage is a strained, "That's great, Dad." And so, it's been decided that the four of you will be living together from now on...