Kuuga:
Successfully complete the game.
Agito:
Successfully complete the game two times.
Kamen Rider 1 alternate:
Unlock Agito, then successfully complete the game again. Highlight Kamen
Rider 1 at the character selection screen and hold L1 + R1 for an
alternate costume.
Kamen Rider 2 alternate:
Unlock Kamen Rider 1 alternate, then successfully complete the game again.
Highlight Kamen Rider 2 at the character selection screen and hold L1 + R1
for an alternate costume.