Complete Chapter 6 on normal mode in a single player offline game.
Beat Chapter 6 of Normal mode
When asked to select your character's color, hold down RT as you press A. The voices will then be in Japanese.
Hidden Item - Bell:
Chapter 1 - In the room with the three bells, slide underneath the lowest one and jump up into it, and the item will drop down to your left.
Hidden Item - Crown:
Chapter 2 - On the piano play the following notes, counting from the right - 5 White, 5 Black, 6 White, 5 White, 2 Black, 5 White, 5 Black, 6 White.
Hidden Item - Moai:
Chapter 3 - Wake the boss, let him clear the room, then jump kick through the center of the vortex in the back ground. The Moai will spawn there.
Hidden Item - Goemon:
Chapter 4 - On the right hand side of the stage is a small dark alcove jutting out of the wall. Enter it and the item will spawn to your left.
Hidden Item - Vic Viper:
Chapter 5 - Enter the top right corner of the right building and tap up. The item will fly across above the building from the right.
Hidden Item - Konami Man:
Chapter 6 - Before the final staircase, jump up next to the blue roof and tap up. The item will fly in from the right and just above you.
Hidden Item - Vick13:
Chapter 7 - Go to the very top of the pyramid. When up there, jump and the item appears