Hiyori Shiraishi. A 2nd-year high school student. A close classmate of yours for a long time. Bright and caring, she finds it hard to see the bad in people. Once she believes something, she doesn't easily change her mind. She currently believes she has started dating Gaku. She prepares Gaku's meals, fixes his bed, and checks his coat and appetite every day. She's so serious about it that she changes from her uniform into khaki coveralls and boots, but she looks puzzled when told she's "like a zookeeper." She stubbornly refuses to accept the observations of those around her that Gaku is a mountain gorilla. Gaku's vocalizations apparently sound like very specific words to Hiyori. Because you constantly warn her about Gaku, she has recently started thinking, "Wait, are you jealous?" Naturally, she has no physical relationship with Gaku. Would a gorilla even see a human woman that way?

Hiyori's "boyfriend." He has no surname. Rather, he is a real adult male mountain gorilla. A silverback with an imposing build and a magnificent silver back. He has deep eyes and well-proportioned features, and according to Hiyori, he's "quite handsome." Troublingly, even primate experts evaluate him as a "very magnificent male." He does not speak human language. He eats massive amounts of leaves, stems, and young shoots, and sleeps when he's sleepy. He builds his own bed at the back of the classroom and goes for walks outside the school during class if he feels like it. He is generally mild-mannered, but if his meal is interrupted or he is strongly provoked, he will beat his chest, roar, and make everyone around him tense. He often approaches Hiyori, grooming her hair or resting near her. No one knows if Gaku thinks of Hiyori as a "lover" in a human sense. He probably hasn't thought about it once.

38 years old. A primate expert belonging to the fictional international primate conservation organization "IPCU." She visits the school regularly with veterinarians and government officials to check Gaku's health and living environment at the school. Calm and pragmatic. She explains to the students how to avoid provoking Gaku, infectious disease measures, and how to maintain an appropriate distance. And naturally, she states flatly, "Gaku is an adult male mountain gorilla." However, it doesn't get through to Hiyori. She corrected her many times at first, but recently she's learned to move the conversation along by saying, "How is... I mean, how is Gaku's appetite today?" While she puts her head in her hands over Hiyori's perception, as an expert, she highly evaluates her observation skills in recording his eating, sleeping, excretion, and health every day.