The game starts with the Shobijin being taken away by an UFO, and saying "HELP, MOTHRA!" The game starts with Mothra Larva hatching from an egg. She can shoot webs to stun any monster (except Godzilla and Hedorah). Mothra can walk north, south, west and east, but the screen locks after going up so Mothra cannot go to places that went offscreen. Mothra can only survive 5 hits of minimal damage, and there are only three lives. However, there are hidden power-ups that restore health that need to be shot with web to be revealed and become obtainable. It is possible to get extra lives by scoring 30,000 points.
After 5 hits, all monsters die. All monsters also die if they hit Mothra, and this results in her obtaining some damage. There is an enemy volcano which shoots boulders and cannot be harmed.
It is recommended to play the game at a slow pace as having many monsters at the screen at the same time can make the game very hard. At the end of a section, there are three gates. You do not need to kill all enemies and you can choose any gate to proceed to the second section of the first level. However, on the second section of the first level, you need to pick the gate to the far right to get to level two. From the second level onwards the game will repeat, but the enemies and power-ups will change locations. The ultimate goal of the game is to get a higher high score.
- Mothra - The main and only playable character. This is Mothra's first video game appearance.
- Gezora - Gezora can respawn 3 times next to some kind of building, and can run pretty fast towards Mothra. Gezora should be taken out slowly and one-by-one to greatly reduce damage received from it.
- Hedorah - Hedorah is located in water and so does not move. Hedorah can shoot a sludge projectile that has a very long range at about one per second. Hedorah cannot shoot straight to the side, so standing by and shooting its side will be the best way to kill it.
- Minilla - Minilla can shoot smoke rings either left or right, which travel at pretty fast speeds. Minilla himself also only travels left or right, making him easy to kill.
- Godzilla - Godzilla can run diagonally and shoots his atomic heat ray at Mothra once close. Godzilla is a hard enemy to kill as he is fast and does not travel straight down. However, he easily can get trapped in a tile, making it possible to shoot from below and easily kill him.