Z/X: Ignition
The story is put from the future. Five"Black Points" suddenly appeared all over the world as portals to parallel worlds. Immediately after, strange creatures began their invasion. These critters are five worlds' inhabitants --exactly the worlds in various time frames. In order to make certain their particular timeframe survives, every one of those five invasion forces battle to wipe out the future time-frames that are other. The key would be one unit.