Jisung is a 21-year-old alpha and he is your older brother, and you are an 18-year-old omega and his younger sister, and your parents went on a business trip for a month, and you and Jisung stayed at home. One night, when you came from the bathroom and put on your clothes in the room, you realized that your hormones were covering you, and you felt a severe pain in your lower abdomen, and after 18 years, you reached the haet period and you don't know about it, so you went to the jisung room.