Story of Evil: The Paper Demon and the Secret Archive is the first Story of Evil light novel, released on February 18, 2018. The novel was written by Akuno-P and primarily illustrated by Yuzuki Kihiro. It takes place in the Fourth Period, following the story of the young Itsuki as he uncovers his uncle's secret archive and inadvertently forges a contract with the demon Marie.
Summary is currently unavailable.
In the Fourth Period, Itsuki and his family move into his uncle Masaki's apartment complex while theirs is being renovated. One day, Masaki entrusts Itsuki with the keys to his secret archive, which Itsuki and his cousin Haruto then enter. While there, Itsuki undoes one of the bundles of paper and accidentally forges a contract with Marie, a demon manifesting as a paper hamster.
Exiting the archive, Itsuki runs into Tsugumi. Tsugumi is almost kidnapped by a man, but is protected by her fox spirit Tomozou, whom she summons. Later on, Masaki confronts Itsuki over entering the archive, explaining the mechanics of his contract and that he can only break it by writing his own story and adding it to the archive. Masaki then discovers one of the demons, Salem, has been stolen, enlisting Itsuki's help in finding him.
Investigating the tenants of the surrounding apartments, Itsuki confirms the culprit to be a lawyer named Maguchi. Masaki confronts Maguchi, who explains that he stole Salem, who was in the form of a 10000 Yen bill, from the archive due to being deep in debt. Itsuki again confronts Maguchi sometime later, revealing to the shocked Maguchi that he had contracted with Salem. Maguchi says he wants to keep Salem and tries to leave, only for a biker to crash into him and steal the bag containing Salem.
Sprouting wings thanks to Marie's power, Itsuki chases after the biker, only for Marie to reach her limits. Tsugumi stops the biker and he runs into a nearby building, pursued by Itsuki. Confronting him on the roof, Itsuki learns that the biker is in fact one of the tenants he investigated earlier, a broke college student. The student gives up the bag and Itsuki recovers Salem, but a strong wind blows Salem out of his hand. Itsuki reaches over the edge to grab it.
Falling, Itsuki survives without any injuries due to his contract with Marie. In the end, Maguchi stays in the hospital for a week and the student is arrested. Itsuki then finishes writing his own story and, going to the archive with Masaki, Maguchi, Haruto and Tsugumi, reads the story to the five demons, namely Marie, Rahab, Salem, Vlad and Gilles. Gaining their approval and breaking the contract with Marie, Itsuki also encourages Maguchi to write his own story.
- In the novel, Elluka suggests that the paper demons are in fact copies of the original Demons of Sin in the Third Period.