Hiromi is a teenage girl from an all-girl school who meets Hideo in the 'Sea of Trees' at the base of Mount Fuji. As first, she mistakes him for someone contemplating suicide and comforts him, after which the two become close friends.
She has a boyfriend who she simply acknowledges as Shinji, though she hasn't seen him since the outbreak.
Later, she is infected by a zombie baby but still retains most of her personality. However, at times she starts to see the world as some sort of child-like vision, viewing people as off-putting stuffed animals. After being infected, her strength increases substantially.
During their refuge at the Outlet Mall, Hiromi is shot in the head by a nail gun. Afterwards, Oda is able to use her knowledge as a nurse to remove the nail and Hiromi surprisingly makes a complete recovery, from both being shot and her infection. She loses all the superficial symptoms of her infection, such as protruding black veins and bloodshot eyes, but retains much of her superhuman strength.
