Shuujin to Kamihikouki: Shounen Paradox

The story starts on April 21st, with him narrating the story. He was prisoner number 420; and briefly talked about the existence of "happy ends" negatively thinking about the world. Number 420 (his real name is not yet revealed nor will it ever be, for everyone addresses him as number 420) was then led to his cell by Kaimural (Kaito) where he found...