1x11 - D_Cide Traumerei the Animation

It was his best friend Murase who was handing out Somnium Drops to the students around him. Just when Ryuhei thinks he has been betrayed, a masked man from the cult appears and defeats him with a single blow. Unable to shake off the awe of his overwhelming power, Ryuhei reminisces about his days with his brother Junpei, who was killed by the man. And with the help of Rando's words, he arrives at the fact that his brother was connected to Troy Merai.