Inertia is one of the primary characters in the chapter and feature film "Land of Illness".

Inertia is a well-mannered girl who first appears in the hospital that Kino is requested to visit, reading a letter. She is described in the novel as a girl with pure white hair, long blond hair that touches the bed when she is in a sitting position, blue eyes and a thin face. Instead of a hospital gown, she wears pajamas with a red and blue tomato pattern, with a pink cardigan on top.

She is in correspondence with a boy who lives in an undeveloped land, and wishes to see him when she recovers from her illness.