About “Marimo Moss Ball -VS- Invasive Alien Species”

Marimo Moss Ball -VS- Invasive Alien Species (Marimo -VS- I.A.S) is a Marimo Moss Ball themed game.

Game on Steam "Marimo -VS- I.A.S"

Coming Soon page was released in Steam


A side-scrolling shoot’em up game that cute Marimo moss balls fights ferocious alien species in the future Lake Akan where the environment has changed drastically.

Fight with lock-on shots that can track up to 6 enemies appearing from the back of the screen at the same time, and forward charge shots that can penetrate enemies and enemy bullets.

Defeating many enemies with one attack will increase the score you get, and the final score will change greatly depending on the order in which you defeat the enemies.

Platform to publish

  • Steam(Windows/MacOS)
  • Tablets and Smartphones
    • App Store(iOS)
    • Google Play(Android)


※These images are under development. These may differ from the actual game screen.

マリモVS外来種 SS1
A flock of signal crayfish approaching

Marimos that survived only a few

Large signal crayfish attacking

Repel enemies at once with lock-on shots!

Destroy the enemy with a penetrating charge shot!

Mutant sea creatures also invade

Mutant individuals who have acquired new abilities attack Marimo!

A marimo invading the burrow of a signal crayfish

Can Marimo survive in the dens of alien species?

Game Manual

Basic Control

Game Mode


  • Start: Play through up to 6 stages
  • Practice: Mode to select one stage and play
  • Tutorial: Mode that you can check how to play the game
  • Option: Various game settings
  • Archive: Bonus menu that you can see stories and information on alien species
  • Ranking: Global high score ranking


For inquiries about the game, please send from here.

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