Yuuta, a illegitimate child, born into a world much different from your own. They are unable to find the child's parents or anyone who hosts their DNA.
This child mystery has been held a secret from the rest of the world, but not any more. Yuuta had been sent to a ordinary high school, unaware of the worlds general culture. Things would get pretty interesting.
A peek into the diary of Yuuta may give you a clue of what's going on. . . .