A war has begun on the planet of Zeon. Unten is the last of the Beorns, and Doomulus Grime is the last of the Doomuli. Doomulus Grime wants to destroy Unten, but Unten wants to save Doomulus Grime because they are both the last of their species. However, Doomulus Grime's GigaDrill causes the planet to split into eight different pieces. Unten must reform the planet and save Doomulus Grime before it's too late.
In the middle of the game, Unten visits Chief Dongorio, who tells Unten about his plans to build a rocket ship in case Zeon is destroyed during the war.
At the end of the game, Doomulus Grime reveals that his life source is connected to Zeon, and he needs to destroy himself, so he must destroy Zeon as well. Unten tries to stop Doomulus Grime, but he ultimately destroys Zeon, killing himself. Unten is saved by Chief Dongorio in the rocket ship. They leave the remains of Zeon in search for a new planet.
After Golden Ring, Inc.'s game, Unten: Mistaken Time, which was, even to Golden Ring, Inc., probably the worst video game in the series, so they gave up on Unten games. However, after Fissure (2014) was announced, they decided to try one more time with a game in That One Series With a Long and Uninteresting Name That I Do Not Wish to Remember. The game was originally going to be called Unten 9.
In February 2014, they announced that after Mistaken Time was released, they were going to start working on another game in the series that was better than the last one they made. They also announced the name of the game, Unten 9, and said that they were working on a redesign for Unten in the game, and three new playable characters in the series named Crali, Brolt, and Tomec. They also announced that neither Zerita nor Netnu would be playable in this game.
When asked if they were going to make another video game in the series, Blue Jay of Lightning replied, "If Unten 9 (the original name of the game) gets positive reviews, we'll look into making Un10."
- Despite being called the ninth game in the series, it is actually the eighth. This is because it was created after the Fissure reboot, but since that was turned into a somewhat separate series, both the ninth and eighth spots are still open, if a game in the series is created before or after this game and before the tenth game.