Epsilon3 is a sci-fi shooter with role-playing elements. The inhabitants of the planet Mu are planning to eradicate all organic life in the universe. To counter that, humans initiated project Epsilon3, sending the most skillful mecha fighter to three cities that must be liberated at first. The player can choose to start in any of the cities, which vary in difficulty. In spite of being called so, the cities in reality mainly consist of vast wilderness areas with a few abstract blocks representing non-interactive buildings.