Justin was a boy that Echo liked.
He appeared in an episode when he and Echo where partnered to do a play for their homework, Adam knew Echo liked Justin making him jealous of Justin. Adam spied on them as they did their romantic play where Justin was a knight. He lashed out with his sword when they where practicing their play ( nit knowing was hurting Adam under his invisibility cloak). Echo ( because she liked him) says she thought he was interested in her but he replied saying that she is out of his league upsetting Echo.