The story takes place in Huanli (the Year of Dazzling) 3015. D'natia and Kōran, two countries fighting for supremacy, are causing the world to be torn apart due to the constant war. Amidst the strife is the island country Nil Kamui, which has lost its independence. Red Dragon, the guardian god of Nil Kamui, goes out of control. Will the island country be able to regain its independence?
Chaos Dragon is based on the role-playing fiction project Red Dragon, a story which was created by five notable writers: Gen Urobuchi, Kinoko Nasu, Izuki Kogyoku, Ryōgo Narita, and Simadoriru (member of the Stripe Pattern doujin circle). The results of their tabletop role-playing game sessions over six days created material for a seven-volume light novel series.