Monster World mode:

Successfully complete the game in story mode.

Monster Grave mode:

Successfully complete the game in Monster World mode.

Violence Rock mode:

Successfully complete the game in Monster Grave mode (all monsters).

Ultraman Returns mode:

Successfully complete the game in in Violence Rock mode with the
top score.

Survival Mode:

Successfully complete the game in Ultraman Returns mode.

First Monster Set:

Successfully complete the game in story mode.

Second Monster Set:

Successfully complete the game in story mode twice.

Third Monster Set:

Successfully complete the game in Ultraman Returns mode.

Alternate ending sequence:

Defeat Z-Ton with physical attacks, without using the Spacium
Ray.