Hajime Aoyama lives next door to Satsuki and Keiichirou Miyanoshita, meeting them when they arrive in their mother's hometown. His immediate observation of Satsuki's undergarments as she lies down sparks her instant anger. Standing between 4 feet 9 inches and 5 feet 4 inches, he has black hair, tan skin, and brown eyes. His typical outfits include dark blue sneakers with cargo or khaki pants, a yellow graphic t-shirt, and a teal green jacket, or black sneakers with indigo pants, a mustard long-sleeve shirt, and a two-tone pea green and cream jacket-vest. Hajime exhibits a distinct preoccupation with viewing female classmates' undergarments, especially Satsuki's, frequently attempting to look under her skirt. He openly discusses this habit. Despite this tendency, he shows sincere concern for Satsuki's well-being, apologizing after causing hurt and displaying worry during perilous events. He shares a close friendship with Leo Kakinoki, bonding over paranormal investigation; together they initially introduce themselves as "Ghost Hunters" while helping Satsuki search for her missing cat in an abandoned school building. Hajime also develops a protective, brotherly bond with Keiichirou. Though often cowardly when facing supernatural threats, Hajime proves reliable within the group during ghost encounters. He actively contributes to resolving paranormal incidents alongside Satsuki, Leo, Momoko, Keiichirou, and the spirit Amanojaku possessing Satsuki's cat. His actions in these crises reveal underlying courage and resourcefulness. A recurring pattern involves him teasing Satsuki while consistently supporting her, creating a complex dynamic where mutual romantic feelings are hinted and confirmed by the series creator, though unaddressed within the narrative. Hajime attends the same class as Satsuki and Leo. He enjoys playing video games and peppers his speech with pop-culture references and slang, particularly in the English adaptation. His dialogue often features crude humor and sexual innuendo, such as claiming to have lost his virginity to his babysitter or making exaggerated statements about dangerous situations. He participates in confronting spirits unleashed by urban development, utilizing knowledge from Satsuki's mother's ghost journal. His role includes direct assistance in exorcisms, frequently overcoming his fears to aid the team. Later, he joins a broader group known as saviors to combat entities like Nurarihyon and Ohma, working with allies including Hanyuu and Eua to rescue kidnapped classmates.