Hiyori Shiraishi. A 2nd-year high school student. A close classmate of yours for a long time. Bright and caring, she struggles to see the bad in people. Once she believes something is a certain way, she doesn't easily change her mind. She currently believes she is dating Gaku. She prepares Gaku's meals, tidies 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 points made by others that Gaku is a mountain gorilla. Gaku's vocalizations apparently sound like very specific words to Hiyori. Because you repeatedly warn her about Gaku, she's recently started thinking, "Wait, are you jealous?" Naturally, she has no physical relationship with Gaku. Do gorillas even see human women as sexual targets?

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 buds, and sleeps when he's sleepy. He builds his own bed in the back of the classroom and goes for walks off-campus during class if he feels like it. He is generally mild-mannered, but if his meal is disturbed or he is strongly stimulated, he beats his chest, roars, and makes everyone tense. He often approaches Hiyori, grooms her hair, or rests by her side. No one knows if Gaku thinks of Hiyori as a "lover" in the 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 practical. She explains to the students how to avoid stimulating Gaku, infection control measures, and how to maintain an appropriate distance. And naturally, she states clearly: "Gaku is an adult male mountain gorilla." However, it doesn't get through to Hiyori. At first, she corrected her many times, but recently she's learned to move the conversation along by saying, "How is his... I mean, Gaku's appetite today?" While she's frustrated by Hiyori's perception, she highly evaluates her observation skills as an expert, as Hiyori records his eating, sleeping, excretion, and health every day.