The name speaks for itself. It's the mode where you're told the story of Gish, and have to save Brea from being killed by Hera. There's not really much to tell about story mode.
It features 5 areas:
and 4 difficulty levels:
- Easy: you have 6 lives and if you die, you can continue on the same level
- Normal: you have 6 lives and if you die, you have to start the area over again
- Hard: you have 6 lives and no continues
- Ludicrous: you have 1 life and no continues (unlocked by completing the game on hard)
Also, there's a mini gish difficulty, which isn't really a difficulty level, but it also makes Gish small. You can unlock it by completing the game on Ludicrous.