One cannot be jealous if one does not know what the other really has.
Its like you can't feel jealousy towards someone with a FuckMaster9000 if you haven't really felt what its like to have its equivalents.
Well people of the comments, if you re-read the comic from the start, GUY has his eyes out for Douki-chan. Even the maid outfit made him think og Douki-chan wearing it.