Hard Mode 5 is impossible. Hard 3 is playable, might need to try the stages once or twice before getting the hang of it, but it can be done.>>9523594
Not sure if this is how, but I got it by going into the Omake battle in the Training section, and asking this one guy to increase Hakuoro's movement speed a bunch of times. After a while, he'll say that he wants to give you a challenge or something like that. Accept, exit back to the title menu, and you'll have Hard mode 4 & 5 enabled.