Step-Brother (2016)

Think about us, not mom or dad. I want to be your man, not your brother. Jae-hee has been with so many men who have made her experience worlds better than her first sexual encounter. She was beginning to get tired of men when her mother got re-married with a man who has a son named Yoon-jae. Jae-hee is attracted to him. In the end, they fall for each other and become something more than 'brother and sister'. Then one day, Jae-hee's mother gets pregnant and things get complicated...