Tenebrae is a horror adventure set in a fictional futuristic place called New Island City where a huge incident occurred involving multiple people, some of whose stories the player can experience by playing through each of their perspectives. This game is a first out of planned but cancelled four episodes, and though each episode work as a standalone story, they all share the common core which helps bind the overall story.
In this first episode, the story follows a reportage writer, Seiji Inugami (犬上 征爾) who one evening receives a phone call prompting him that something big is going to happen in New Island City. While reluctant to take a commission to collect the data onsite at first, he ends up coerced into agreement by the caller who blackmails him with something from Seiji's past which he was part of 15 years ago where he witnessed something he shouldn't have. On his way to the city, he ends up meeting his old friend, police detective Kaoru Saegusa who is working on a case involving a series of disappearances. While friendly chatting, they hear what sounds like a sea of screams in the distance. As they look toward it, they see a huge black fog enveloping the area. Thus, the search for answers and uncovering the mystery behind it begins.