A foreigner who knows and loves Japan more than most Japanese people, Koizumi Yakumo is an English Literature instructor at Tokyo Imperial University and enthusiastic mononoke researcher. He is loud, dramatic, and overly familiar, but he acts like a true gentleman and can dissolve tension quickly.
His left eye is a prosthetic: he lost it when he was a child, and from that point on he could no longer see mononoke. His frantic attempts at ghost spotting are a reflection of the feelings of loss and despair he felt at that time.
