Story Mode

Story Mode is the official story of the game, The One Billion Survivor.

Normal Mode
The Normal Story Mode is the easy version of Story Mode. The stages are Ignition Starts, Tsukematsukeru, HTTP, Escape, Cross Time, Inkantation DX, Party Island and Further Flew Far Faster Ference. The extra final boss battle is not included.
 * Link:

Extra Story Mode
Hard Story Mode or Extra Story Mode is a harder version of Story Mode. This version is added in update 2.00.0. The final stage is different called Ghost Rule. The extra final boss is included. Every stage ends with "EX", standing for "Extra". For example, level 1-1 is 1-1 EX.
 * Link:

Trivia

 * Prior to version 2.01.0, Stage 8 EX's song is Ultimate Future Mikutron, but they changed to "Ghost Rule" as of version 2.01.0.
 * The Normal Extra Final Boss is removed in version 2.02.0 of The One Million Survivor, because the test is finished.
 * Finishing the Normal Extra Final Boss unlocks Pump It Up XX, Glitter Force and Glitter Force DX or Glitter Force Doki Doki.
 * During the Hard Extra Final Boss in version 3.01.0, the boss may fire up to 70 lasers instead of 40.