In the year 2044, Earth was invaded by a group of huge biological entities only known as "Devil Parasite". They basically rampaged through the Earth like Godzilla and killed off over 80% of the world's population. Now, two years later, in 2046, the remaining humans have gathered together to fight back. A secret research complex was developed to research biological weapons to fight these creatures. You are basically the head of this organization. At this facility, you prepare your biological weapons, which are basically huge variations of the "Devil Parasite" and train the three pilots, Alisa, Casty and Lerike in developing their physical, mental, piloting, as well as their H abilities. To prepare for the inevitable confrontation with a Devil Parasite.

[From animedensetsu]