Natsuko Asai is a supporting character in the original video animation adaptation of 3x3 Eyes. She is a friend of the protagonist Yakumo Fujii from their junior high school days. Even after they parted ways, she never forgot about him. Later in life, she becomes a high school teacher, demonstrating a responsible and dedicated nature. Natsuko is characterized by her warmth, loyalty, and kindness. She reconnects with Yakumo during the events of the story, showing genuine concern for his well-being and a willingness to support him. Her role in the narrative is primarily that of a link to Yakumo's ordinary past, providing a sense of normalcy and grounding amidst the increasingly supernatural events. Her relationship with Yakumo is built on a foundation of long-standing friendship and mutual respect. Natsuko does not possess any supernatural abilities and remains an ordinary human, which highlights the contrast between the mundane world and the dangerous, mystical realm that Yakumo has entered. Her development is limited, as she serves mainly as a reminder of the life Yakumo left behind, but her steadfastness and caring attitude underscore her nature as a reliable and compassionate person.