Clear Subspace first, then either Clear Classic Mode with anyone or go through the new door in The Forest (Or whatever stage Link & Yoshi started in) in Subspace to fight him.
Or you could do 400 Vs. Mode fights, either or.
And before I forget, who is Ryu? I think he was Trucks friend but he's unfamiliar to me~
My Creations in Modnation Racers! Check zhem!
http://community.modnation.com/en-us/players/IvoYaridovich/creations