Episode 2: Kazuya defeating 99 trained martial artists to learn how to transform.
But that's not how he learned, in the end. Martial artist #100 was his Old Master, who gets his CMOA when he steps up as the last warrior Kazuya must face. Kazuya easily beat the other students, but the master curbstomps Kazuya in seconds, and the terror Kazuya feels falling off of a cliff brings out the survival instinct that triggers the transformation. Somehow, this lets him Zen up his Rider powers whenever he needs to from then on.