故事背景（序）

Nobady knows why the aliens came to the Earth.Maybe their planet had a big war and some of them drove the spaceship to run away.They then find the beautiful Earth and decided to land on it.However,when they landed,the US army found it and used something special to attack the spaceship.It crashed down and made a big explosion.Of course,it was in pieces.The noise brought many local people to come.The army did not want anyone else to know this,so they took the wreckage and aliens away and told people to forget everything.The soldiers sent the death aliens to the scientists to observe and made a lot of inventions.The only living alien now may be in the Area:51,works for the US army.