Seiko Ayase is one of the main characters in DanDaDan, a high school girl born with powerful psychic abilities inherited from her grandmother. With her distinctive snow-white hair often worn in a top knot and red rectangular glasses, she stands out both visually and through her serious, no-nonsense personality. Initially a loner who believed only in ghosts and spirits, she meets Okarun and they form an unlikely partnership.

Seiko's psychic powers allow her to sense, see, and combat supernatural entities that most people cannot perceive. Despite her tough exterior and tendency to kick first and ask questions later, she gradually opens up through her adventures with Okarun. Her grandmother trained her in the ways of the occult, preparing her for the chaotic battles against aliens and spirits that define the series. Her combination of psychic abilities, martial arts skills, and fierce determination make her a formidable protagonist in one of the most unique supernatural action series in recent manga history.