The first scene when Hakuryuu is introduced, and when Judar's name is revealed for the first time, it is made very clear that Judar prefers Hakuryuu over Koutoku and that he would like to take him to a dungeon. And that he's been suggesting it for some time. Hakuryuu isn't really okay with that idea for now.
(As a complete side note, it's kind of funny/interesting to me that Judar is introduced eating a peach, and there is also one next to him that he has only taken one bite of. In ancient Chinese literature, "bitten peach" meant homosexuality. And Kou is of course based off of ancient China.)