Seol-ah is having a small party to celebrate her 100th day with her boyfriend Do-jin. As the party went on, Seol-ah suddenly fainted and collapsed. Do-jin tampered the drink with a drug. Do-jin invites his friend Dong-joon to film him sexually harassing a dejected Seol-ah with a camcorder.
Seol-ah, who opened her eyes the next day, is shocked and tries to escapes the house when she sees Dong-jun lying next to her, but is forced to have sex with Do-jin, who has changed 180 degrees. Seol-ah, who later felt violated by Do-jin and Dong-jun, decides to leave for Japan.
With her mother's remarriage, Dong-jun lives in his stepfather's house while they are on honeymoon. However, on the first night of living in his stepfather's house, he witnessed his step-siblings, Seol-ah and Do-jin, having sex. Seol-ah and Do-jin are not brothers or sisters, but Dong-jun is shocked at the thought that they are brothers and sisters. That night he dreamed for the first time in years and the next day, Do-jin leaves early and only Dong-jun and Seol-ah were left at home. Dong-jun feels burdened by Seol-ah’s kindness. After a while, Dong-jun, who returned from exercising in the yard, finds Seol-ah taking a shower with the door open. Seol-ah asks Dong-jun to wipe her back. Since they have become families, she suggested for them to shower together, and they had sex.
Sang-woo is suffering from erectile dysfunction and premature ejaculation, because he is worn out from Ji-eun's strong sexual desires. Then, one day, Ji-eun sends him to a treatment center and the specialist is no other than his ex-girlfriend, Hye-ran. They bicker about past things, but in the end agree to start treatment. Hye-ran manages to bring back Sang-woo's sexual desires with lower body exercises, massages, sexy dances and mental therapy. On the day he is discharged from the center, Sang-woo and Hye-ran share a last kiss, but end up wanting each others' bodies...
Sang-woo goes home feeling down after being dumped by Hye-ran. At home, he is surprised to see a strange woman doing the chores. Ji-eun introduces herself as the new housekeeper. Sang-woo feels attracted to Ji-eun, who is open-minded and good looking, but is disappointed to see her act as his father's 'partner'. Then one day, Sang-woo's father passes away while having sex with Ji-eun and Sang-woo becomes an orphan...
