Ed's Links
At first, Ed is jealous of how close Kouryuu is to Theo. Then Kouryuu assured him about who he is in relation to Theo, and correctly deducted Ed's feelings. He's not jealous anymore, but he dislikes Kouryuu and they like to one-up each other with arguments. They are actually more alike than they think, but in somewhat opposite ways. When he's not arguing with Kouryuu, he sees Kouryuu as an annoying but reliable ally that sometimes says very good opinions.
He dislikes Ed. Mainly because they often argue (as the two in the group with the most amount of braincells) but also because Ed seems to be Theo's number 1 stress cause. Ed often hides things and doesn't get straight to the point--Kouryuu gets irritated by it. However, he acknowledges Theo's loyalty to Ed and tries to lead their relationship in a good path. He's also willing to get along with him when he has to, even if it's in a playful, passive agressive way.