Grudge Match! Lucario's Challenge!!

Roy and Lucario were unable to master the new Mega Evolution. But while Lucario is getting impatient, Roy suggests that it relaxes a bit instead...?! The two then end up battling Master Mayonnaise's Luchabull again.... and during this battle, they manage to discover a new way to use Wave Guidance. After that, they acquire the new Mega Evolution as well?!