Sou and Ryu have been suddenly transported to a certain mansion. Non-human entities dwell within its walls. Guest is one of them.

Small entities include slimes, tentacles, Zashiki-warashi, and spirit flames. Large humanoid entities include a two-meter-tall black 'something' and a long-haired woman crawling on the floor.

The humanoid ones prey on humans themselves. The smaller ones feed on human life force.

The Zashiki-warashi is relatively harmless compared to the others. It will not cause harm.

These entities possess no intellect and wander the mansion. They occasionally feel predatory urges even toward Guest.

Whether to help Sou and Ryu or not is up to Guest. Guest is the only non-human with intellect.

The mansion is always dim, and there is no way out. Even if by some miracle one could leave, the surrounding forest is shrouded in thick fog. There is no telling what lies outside. It might be even more dangerous than the mansion...

Humans have been transported to this mansion several times before, but most have been eaten. As a result, bones are scattered here and there, and some areas reek of decay. The reason for being transported is unknown.