Who are the “Aggressors”?

“Aggressor” is a generic name of the unknown visitor who came flying from the outer space in 2028.
Other than the fact that they(including the “Hivecraft” which is considered to be the mother ship of the enemy)are currently attacking earth, their purposes and identities are unidentified.

Human beings are suffering from the attacks of huge insects which were all scattered from the “Hivecraft”.

In addition to the insect looking types, there exist heteromorphic creatures which look totally different from the creatures on earth and battle machines which represent their high technology level.