Nightmare Detective follows a mysterious detective who has the ability to enter people's dreams and help them face their nightmares. When a series of violent crimes occur in Tokyo, the detective is called in to assist the police. As he delves deeper into the dreams of the victims, he uncovers a web of hidden truths and dark secrets. With the clock ticking, he must navigate the surreal and dangerous dream world to catch the killer before more lives are lost.

In Nightmare Detective 2, a detective with the ability to enter people's dreams is hired to solve a series of mysterious suicides. As he delves deeper into the nightmares, he discovers a dark and twisted world filled with secrets and danger.