What if he really was that jaryuu just that after lazing about for 5000 years he became fat and forgot about himself due to age problems? And after reiko was sent to him he transferred all his powers to her unconsciously but that is just a theory...
@mikoreimu He is Jaryuu, an immensely powerful dragon with power rivaling that of a demon lord. Summoning a bubble tea is a minor inconvenience for him, show some respect.