Far away... In a system so distant that the light from its stars would never reach Earth... The war was coming to an end.

Exelica and Crueltear - a humanoid weapon system called Triggerhearts developed by CHILDA, an interplanetary defense organization - were sent to join the fight against an autonomous combat unit known as the Ver'mith.

In the midst of the battle, just as they gained the upper hand over Ver'mith, Exelica and Crueltear were accidentally sent to Earth using an emergency teleportation gate activated by Ver'mith.

The wounded Triggerhearts found themselves on an unknown planet, lacking the strength to return home, and were disheartened because they did not even have the means to learn the outcome of the battle.

They had just recovered from their injuries and were finally beginning to consider Earth a haven... when this happened.

A nightmare filled the sky. The remnants of the Ver'mith forces arrived. The gate opened again...

Although the Ver'mith forces departed at the same time as Exelica and Crueltear, the instability of the gate caused a delay in their arrival.

The Ver'mith have chosen Earth as their new base of operations. The invasion has begun. Exelica and Crueltear know they have no choice but to fight to protect their new home.