Azumanga Daioh Codes -

Omake sounds:
Successfully complete the game as any character under the normal difficulty setting.

Omake background music:
Successfully complete the game with all characters under the normal difficulty setting.

Omake pictures:
Complete each of the following tasks to unlock a picture for that character: successfully complete story mode under the normal difficulty setting; successfully complete sudden death mode; successfully complete story mode under the hard difficulty setting. To unlock the picture featuring all characters, successfully complete story mode under the normal difficulty setting with all eight characters.

Hard difficulty:
Successfully complete the game as any character under the normal difficulty setting.

Play as Yukari:
Successfully complete story mode under the normal difficulty setting as Chiyo, Kagura, Osaka, Sakaki, Tomo, and Yomi.

Play as Nyamo:
Successfully complete story mode under the normal difficulty setting as Yukari without using any continues.

Fight against Nyamo:
Play through story mode without losing any times to face Nyamo as the final Boss.