When I was a high school student, my sister was a sexy friend who kept me from falling asleep with all kinds of delusions every night. Min-soo's thrilling delusion catches fire after she accidentally meets her naked sister at home. After becoming an adult, Minsu and his friend Yong Joon get a job at a sister company. From her sexy friend, Minsu's secret work towards her, who is now reunited as a sexy female warrior, begins...

Hyeri and Ji-yeon are friends in the same neighborhood. They have a son to go to the army after some time. One day, Min-gu, who was playing at Jun-suk's house, sees Jun-suk's mother Hyeri in the shower and gets excited and hits her. Hyeri, who initially resisted, gave up resistance to Mingu's power, and after that day, the two develop into sex every time they have time. After a few days, Ji-yeon, who accidentally witnessed her son Min-gu and Hye-ri having sex, begins to seduce Hye-ri's son Jun-seok.

Hyeon-soo manages a hostel run by his friend Jeong-ho. It's a hostel for foreign female students. There is a Korean-American from LA, a Japanese who's here to learn Korean out of love for K-Pop and his friend's sister who just happens to be there. These women are very outspoken and Hyeon-soo and Jeong-ho fall for them.