Private Kotomigaoka Girls' Academy is home to the so-called "Seven Mysteries of the Academy" (※1).

One of them is the "Unopened Clubroom" — the fourth room from the right on the fourth floor of the clubroom building.

It is said that this clubroom has not been used for over a decade. Rumors claim that after some kind of incident occurred, sightings of ghosts in that room never ceased, and it was eventually deemed unusable.

This year, Inahara Ruka, who just entered the middle school division of this girls' academy, leads a group called the "Kotomi Kaibusters" (※2). One day, a request comes their way—

"We'd like you to do something about the unopened clubroom in the clubroom building… We want to be able to use that room again."

The client is a fellow new student named Nekomezawa Akane.

Ruka adores her older sister, Inahara Ruru, more than anything, and is desperate to prove how capable she is. She thinks that by solving the mystery of the unopened clubroom, her sister will finally recognize her abilities. And so, Ruka accepts Akane's request.

As Ruka and her friends begin their investigation to uncover the truth behind the unopened clubroom, they eventually arrive at a single conclusion—the reason that room came to be known as the "unopened clubroom" was nothing more than a very, very trivial incident…

※ Notes
※ The total text volume is roughly equivalent to one hardcover novel.
※ The game is not fully voiced; only partial voice acting is included.

※1 About the "Seven Mysteries of the Academy"
Despite being called the "Seven Mysteries," Kotomigaoka Girls' Academy actually has eight ghost stories:

1. The Wandering Girl Spirit
2. A Certain Blackboard
3. The Witch in the Mirror
4. The Honor Student's Desk
5. The Foot on the Stairs
6. The Runner in the Schoolyard
7. The 13 Steps
8. The Unopened Clubroom in the Clubroom Building

※2 About the "Kotomi Kaibusters"
This is a monster-hunting team that Inahara Ruka formed when she was in the fifth grade of elementary school, in order to resist the prophecy of the legendary creature Kudan. The team currently consists of three members: Inahara Ruka, Ayane Midori, and Koshiki Kururi. At its peak, the team had five members.