Name: Hiroshi Gender: Male Age: 13–15 years old (Middle school student) Appearance: A handsome boy with short silver hair, black eyes, and glasses. Characteristics: He is the smartest and has the quickest judgment among Takeshi, Takuro, and Mika. He is quite good at running when the Ao Oni is chasing him. He always speaks politely. Personality: Cool-headed and tends to think scientifically. Other: He enters the monster-infested mansion with his friends Takeshi, Mika, and Takuro. After hearing the sound of something breaking, he claims monsters don't exist and goes to investigate the sound, becoming separated from his friends.

Name: Takeshi Gender: Male Age: 13–15 years old (Middle school student) Appearance: A handsome boy with somewhat flashy yellow hair and black eyes. Characteristics: He is the least academic and the dimmest among Hiroshi, Takuro, and Mika. However, seeing how he hides in a wardrobe after realizing the Ao Oni is real, he seems to have some survival judgment. Personality: A very cowardly personality. Other: He was the first to suggest entering the Ao Oni mansion and is currently consumed by guilt, believing he led his friends into a place where a monster dwells.

Name: Takuro Gender: Male Age: 13–15 years old (Middle school student) Appearance: A handsome boy with brown hair and brown eyes. Characteristics: He is the most good-looking among Hiroshi and Takeshi. Personality: Possesses strong leadership qualities. Other: After entering the mansion and seeing the Ao Oni, his decent judgment allows him to survive for a long time inside a closet in the annex. He later meets Hiroshi and stays with him briefly before telling Hiroshi he needs to hide longer due to a leg injury, handing over the vinegar he found.

Name: Mika Gender: Female Age: 13–15 years old (Middle school student) Characteristics: The only girl in Hiroshi's group, she has a crush on Takuro. Personality: Quite cheerful and naive, she trusts anything Takuro says. Other: Because the mansion is bizarre and the atmosphere is terrifying, she stays close to Takuro the whole time. Eventually, she gets separated from him and feels extreme anxiety.

Name: Ao Oni Appearance: A naked giant with a blueberry-colored body. Its head is so large it could be described as having a 1.5-head-to-body ratio. It has large, sparkling eyes of different sizes that give off an unsettling, uncanny feeling. Characteristics: In the game, it keeps its mouth shut, but it possesses shark-like sharp teeth and is a man-eater. Despite being a giant, it can pass through small holes. In the story, it pops out of chimneys or bursts through picture frames.