Title: Placebo - Short Story Edition
Woo-yeon and Woo-jin are step-brothers and have been since they were young. For the same length of time, they have also had a vitriolic relationship, with Woo-yeon vehemently bullying and mocking Woo-jin any chance he gets. This never dissuaded Woo-jin, who stayed right by Woo-yeon's side, no matter how cruel he might be. Woo-yeon revels in Woo-jin's loyalty, taking every opportunity to pick on Woo-jin.
Woo-yeon doesn't realize that Woo-jin has developed the power of hypnosis and has been using his power to control and dominate Woo-yeon. When Woo-jin finally holds the reins, Woo-yeon will receive every ounce of punishment he has earned over the years. But it isn't in private. It will be in front of the two people he would never want to be seen by: their parents.