Ski Air Mix Easy mode
Wait until the demonstration sequences has completed. Then, press Select, Circle, X, Triangle, Square. If you entered the code correctly, the title screen will turn red. Now easy mode will be selectable.
Bonus character and board
Beat all courses with “Best Time” and “Action Point” ranked at number 1.
The image featured at the top of this post is ©The Legend of Heroes: Trails of Cold Steel III key art / Original