It is unknown how long they have existed. Some sightings date back to 2017. But in the year 2031 Humankind was replaced as the dominant species on Earth.
They are known only as The Blue. Many believed that the Blue were created by a rogue nation as a weapon of mass destruction. But it soon became all too evident that this was not the case. These monstrous insect-like creatures now exert their terrible will upon the planet. As a result, the remains of the human race have fled into outer space to escape the infestation of the Blue.
Suddenly awakened after 22 years in suspended animation, Yuji Kaido finds himself thrust into a nightmarish reality. Yuji soon learns that the very survival of the entire human race rests in his hands.
(Source: Funimation)
— Description from AniList community (anilist.co).
