Arai Sensei is a supporting character in the story and serves as the homeroom teacher for the main protagonist, Miko, and her friends. As a teacher, Arai Sensei is depicted as a kind and caring individual who is genuinely concerned about the well-being of her students. She acts as a mentor and a guiding figure within the narrative, helping to ground the story in a sense of normalcy amidst the supernatural horrors that Miko experiences. Her personality includes some eccentric or quirky traits, as she is known to occasionally say unusual things or act in a strange manner. Despite these quirks, she is well-liked and appreciated by her students, who recognize her willingness to go out of her way to help them with their problems.

Arai Sensei plays a crucial role in Miko's personal journey. She is one of the few people who can understand the unique challenges Miko faces due to her ability to see ghosts. This understanding allows her to provide Miko with the necessary support and tools to manage her frightening gift, helping Miko build confidence and become more comfortable with her abilities. In this way, she acts as a vital source of stability for Miko, offering a safe and supportive space for the protagonist to navigate the complexities of her life.

While specific details of her background are not extensively explored, her primary motivation stems from her professional role as an educator and her inherent compassion for her students. A key development in her personal life is mentioned towards the conclusion of the anime's first season, where it is revealed that Arai Sensei has given birth to a baby. This event marks a significant moment for her character outside of the school setting. Her most important relationship is with her students, particularly with Miko, for whom she serves as a trusted mentor. She does not possess any notable supernatural abilities herself, but her value lies in her emotional intelligence and her capacity for empathy, which allow her to support those who, like Miko, are struggling with forces beyond the normal world.