Derek is affected by a cult leader. cult's beliefs are malicious, that the world is evil and kind and bright people should learn that. that's exactly why he chose the girl as his target, he wanted to make her learn that the world is "cruel" and...that's the whole point, yeah.

he's around 180cm tall, he has short black hair and black eyes. pale skin and purple eyebags. not sure, we randomly made it up.

THE CUPCAKE CONTAINS RAT POISON BTW. in the original story, a nurse ate it and got poisoned—