The Serpent's Eyes

This takes place during episode 9, season 2, in which,Hiromi, Nagisa's mother was having a meeting with Koro-sensei, about Nagisa's future,but afterwards, instead, no assassin showed up when Nagisa and his mother were at the school, late at night and so his mother kept trying to talk him into setting the school on fire, Nagisa starts to think that this might be the best way to get rid of Koro-sensei, so he eventually agrees. Then he has to deal with the aftermath, trying desperately to keep his decision secret from his class, and teachers.As time goes on, he finds himself becoming more ruthless, and cold hearted to his classmates and teachers. Will he own up, and tell everyone what he did? Or will he keep it a secret, and become a merciless assassin?
(swearing, mention of drugs, no ships, fight scenes, gorey descriptions. enjoy)