While at school, Taniyama Mai and her friends like to exchange ghost stories. Apparently, there is an abandoned school building on their campus that is the center of many ghost stories. During the story, they are interrupted by a mysterious male figure. The person turns out to be Shibuya Kazuya, a 17-year-old who is president of the Shibuya Psychic Research Company. He was called by the principal to investigate the stories surrounding the abandoned school building. The next day, on the way to school, Mai passes the school building in question. While examining a strange camera she spotted inside, she gets surprised by Kazuya's assistant. Unknowingly interfering with the investigation, Mai breaks the camera and Kazuya's assistant gets injured. Kazuya forcefully hires Mai in order to pay for the camera and replace his injured assistant. From that point on, Mai begins to learn about the paranormal world and the profession of ghost hunting. [Written by MAL Rewrite]

The third season of Dungeon ni Deai wo Motomeru no wa Machigatteiru Darou ka. When Bell encounters a frightened little girl in the dungeon, he doesn’t think twice to help. But this simple act of kindness has consequences. The girl is a monster and proof that monsters can be eerily human. And not everyone can accept this... (Source: HIDIVE)

An OVA summarizing all 25 episodes of season 2.

A large scale catastrophe is occurring across the planet. Ability users are discovered after the appearance of a mysterious fog, apparently having committed suicide, so the Armed Detective Agency sets out to investigate these mysterious deaths. The case seems to involve an unknown ability user referred to as "Collector," a man who could be the mastermind behind the incident.

Trust and courage are put to the test in order to save the city of Yokohama and ability users across the world from the grip of Collector where the Armed Detective Agency forms an unlikely partnership with the dangerous Port Mafia. 

[Written by MAL Rewrite]