The protagonist, Canalière, is an adventurer belonging to a guild. She accepts a request to exterminate goblins and visits the remote village of Slag.

There are two reasons for the mission: To exterminate the goblins that are ravaging the village, and to search for her sister, who went missing into the forest on the same request.

Slag village is a closed village that worships a local deity called the "Forest King." The villagers are somewhat distant and hold a special fear of the forest.

The guilds intermediary gives her a small black box, which he says is a pass to enter the forest. Without explaining its meaning, Canalière spends the night at an inn.

The next morning, as soon as she steps into the forest, she encounters a tattered adventurer. It was one of the extermination party members who had gone ahead.

Deep in the forest, the adventurers had been annihilated. Furthermore, she witnesses goblins trying to abduct a female adventurer.

But what was strange was that the goblins were speaking human language.

What was supposed to be a simple extermination mission turns out to be something else entirely, with a different intention and order existing deep within the forest. The whereabouts of her sister, the meaning of the black box, and the goblin who manipulates words—

Canalière steps closer to the truth of the forest.