Taito Memories: Volume 1 All hidden games
At the title screen, press L1, R1, R2, L2, Select, Start to unlock Bubble Bobble, Cameltry, Kiki Kaikai, Metal Black, and Syvalion.
Bubble Bobble
Play all default games at least one time to unlock Bubble Bobble.
Cameltry
Accumulate at least one hour of game play time in Lunar Rescue, Ah Eikou No Koshien, Alpine Ski, Cleopatra Fortune, Puchi Carat, and Flipull to unlock Cameltry.
Kiki Kaikai
Accumulate a total of five hours game play time to unlock Kiki Kaikai.
Metal Black
Accumulate at least one hour of game play time in Space Invaders Color, Space Invaders DX, Darius Gaiden, Grid Seeker, and Majestic Twelve to unlock Metal Black.
Syvalion
Accumulate at least one hour of game play time in Elevator Action Returns, Kuri Kinton, Jigoku Meguri, Don Doko Don, Rastan Saga, Fairyland Story, Pulirula, Lightbringer, and Runark to unlock Syvalion.
The image featured at the top of this post is ©The Legend of Heroes: Trails of Cold Steel III key art.