Uno and Masashi have been living happily together for three years. As their lives have stabilized, they have decided to have a child together soon. Today is Uno's ovulation day, the day she is most fertile, and she has prepared many nutritious dishes to help her husband be energetic tonight to create a baby with her. However, Masashi's junior brother, Oki, came to visit in the evening. They had so much fun that Masashi got drunk and they couldn't do anything. The next day, Oki came again, wanting to bring something for Masashi but forgot it at the hotel. With no time, he asked Uno to go to the hotel to retrieve it. When she arrived, he forced himself on her and ejaculated inside her on her ovulation day. That night, she made her husband ejaculate inside her repeatedly to forget about Oki. A month later, he didn't contact her, she wasn't pregnant, thinking she could finally relax a bit when Oki showed up again. He threatened to tell Masashi everything, so she had to listen to him, letting him continue to ejaculate inside her on her ovulation day. And from then on, every month, he would come to impregnate her on her fertile day. This time, Masashi also wanted to impregnate her, but she refused, lying about going to a friend's birthday to spend the night at the hotel with Oki. A month later, she became pregnant, and Masashi was overjoyed to soon become a father. However, she knows for sure that the child in her womb is most likely not her husband's, because they haven't had sex for the past month...