When his mentor is injured, novice linguist Hakaba is appointed to take over the professor's research in the Netherworld! Though Hakaba has studied the languages of werewolves, lizardpeople, and other Netherworld races from afar, this will be his first field experience coming face-to-face with those so many of his fellow humans have dubbed "monsters." Guided by Susuki, the professor's half-werewolf daughter (?!), Hakaba begins his quest for a greater understanding of the ways people of the Netherworld communicate-even if it does get a bit...hairy at times...!

Hakaba’s diverse traveling party, made up of half-werewolf Susuki and lizardfolk siblings Kashuu and Kekuu, welcomes its newest member, the minotaur Moo. Struggling to communicate through a series of wild gestures, guttural grunts, and the gnashing of teeth, Moo eventually gets his point across in Old Werewolf—a language that is new to the linguist at large! Discovering the varied ways Netherworlders communicate grants Hakaba fresh insights into how different species think and interact. And, unbeknownst to him, his human tendencies are being scrutinized just as closely?!

With winter weather fast approaching, Hakaba finally arrives in Utatsu to continue his linguistic research. The diverse residents of the town—and their flexible notions of “private property”—provide ample opportunity to study Netherworld culture and communication from the comfort of his “own” home. Despite having the best intentions, Hakaba must be mindful that human biases don’t negatively affect his attitude toward his new comrades…even when they decide the walls of his newly restored dwelling would make a perfect snack!

After crossing the treacherous snowy mountain, Hakaba's group finally arrives in the human settlement Utatsu where his professor had visited. As he meets humanoids and joins them in hunting in the perilous dark, he grows ever closer to both the inhabitants and understanding their culture.

As spring finally arrives, Hakaba’s party finally finishes their journey to the coast. As they begin their research on the new region, Hakaba is swept into an underwater cave by its residents—who are indistinguishable from fish! Will Hakaba be able to figure out how to communicate with the inhabitants and escape from the cave before it’s too late?