To get Ryumaou on the virtual character select screen, beat SD Hiryu with Ryumaou. After beating it a couple of times you should get the "Skull of Devil King" as a random prize. This enables you to pick Ryumaou at the Virtual Hiryu select screen.
Play as Ryumaou
To play as Ryumaou, you have to earn your way up to the "Ryumaou Tournament", and then beat it.
Play as Bokuchin
To play as Bokuchin you must beat him in a normal game.
On game select go to SD HIRYU. From there fight in the circuit. Platinum characters will make cameo appearances before the championships. Each time you beat a platinum character you win a medal. If you collect all 10 medals you can use the Platinum characters.
For a greater challenge, go to the OPTIONS screen and set the difficulty to HARD, then press RIGHT 20 times. You can now access the VERY HARD difficulty setting. Good luck!
For an easier game, go to the OPTIONS screen and set the difficulty to EASY, then press LEFT 20 times to enable the VERY EASY level.
Defeat Metal Robo Na Hanna
Metal Robo Na Hanna has a very powerful magic. The magic he has prevents him from taking damage, and to make it worse damage normally done to him is done to you!
The only way to defeat him is to use the item "Mr. Virus" which steals his invincibility. The item "strategy book vol. 8" says it steals all powers, but it doesn't. When you get "Mr. Virus" and are fighting Metal Robo Na Hanna use a projectile attack or a projectile secret buster.
Earn nine medals to play in the Ryumaou tournament.
Dark Dragon Claw
Successfully complete the Ryumaou Tournament as Yuka at Rank S with 60 second, two round and normal difficulty settings. Note: You must already have nine medals.
Bokuchin: Black suit
Select Wiler and do his Wiler Bomb any other bomb with a character on Bokuchin. He will wear a new black suit briefly.
Ryuhi: Red belt
Select Ryuhi and do his Super Kinryuha do Robo No Hana. His belt will turn red briefly.
Wiler: Disappearing shirt
Select Wiler do his Ninja Circus. If done correctly, he will not be wearing a shirt while climbing down the stick. However, it will reappear after he gets off the stick.
Learning new combos
Enter practice mode on Virtual Hiryu, Then, hold Guard + C-Right. You can learn some great combos while in free training. For example, to execute Hayato's Ultimate Defense, press Right, Left, Punch, Down, Up, C-Down, Left, Right, C-Down, Down, Up, C-Down.