As an American service dog owner, I looked into this recently! We didn’t qualify in Japan, so my dog has been promoted to pet status.

Other than the requirements for the dog, you also need to prove significant physical impairment and have a disability license issued by the government in order to have a service dog. “Mild” visual/physical disabilities may not qualify, and the disability status has tax and social security implications so they’re very strict and unforgiving. A personal anecdote is a friend who has partial paralysis of one arm didn’t qualify for any disability status even though they have limited mobility, because they can technically do most daily life tasks with their other arm and the paralyzed arm can still weakly function as a supporting second arm when both arms are needed