Gurumin: A Monstrous Adventure Codes -

Original Japanese voice acting
Successfully complete the game, then choose to start a new game. Then, hold + and press , , , , , , , , , , , at the difficulty selection screen. A sound will confirm correct code entry.

Movie viewer:
Successfully complete Boss Rush mode.

Hard mode:
Successfully complete the game under the Normal difficulty setting.

Happy mode:
Successfully complete the game under the Hard difficulty setting.

Alternate costumes:
Complete the indicated task to unlock the corresponding alternate costume. Use the dresser in the corner of Parin's room to change costumes.

Armor: Give 30 Gold Medals to Hyperbolic in Beginner mode. 
Chinese Dress: Get the good ending in Hard mode. 
Kimono: Set the system date between January 1st and 7th. 
Leopard Suit: Get the good ending in Crazy mode. 
Maid Outfit: Can be bought from the vending machine at Spinach Caverns - Shadow Grotto. 
Monkey Suite: Get the good ending in Beginner mode. 
Nurse Outfit: Complete Boss Rush mode in Happy mode. 
Pajamas: Get the good ending in Normal mode. 
Princess Dress: Give 30 Gold Medals to Hyperbolic in Normal mode. 
Samurai Outfit: Give 30 Gold Medals to Hyperbolic in Crazy mode. 
Santa Outfit: Set the system date between December 25th and 31st. 
School Uniform: Get the good ending in Happy mode. 
Swimsuit: Complete Boss Rush in Crazy mode. 
Vampire Outfit: Give 30 Gold Medals to Hyperbolic in Hard mode. 
Witch Outfit: Give 30 Gold Medals to Hyperbolic in Happy mode. 
Work Uniform: Complete Boss Rush mode in Hard mode. 
Workout Gear: Complete Boss Rush mode in Beginner or Normal mode.