In an oral report about personal heroes, Ronnie speaks of his grandfather's dog. Years ago, an Akita puppy escapes his cage from the U.S. to Japan. Professor Parker Wilson finds the pup and decides to take it home when the train station's manager refuses to take it in. Parker only plans on keeping the dog until the owner can be found. Initially, his wife wants nothing to do with the dog. After researching what he can about the dog, Parker names the dog "Hachi." When a potential adopter calls the Wilson household, the Parkers realize that they've grown too attached and turn him down.
While Hachi refuses to act like a normal dog, he soon starts a schedule of following Parker to work each day and waiting around the station for him to return each evening. However, things change when Parker has a fatal heart attack during class.