USA passpot. in Tokyo,Japan for 60 days. I am disabled. Can I get visa the same day? Can you mail it

You can get the visa on the same day, but you have to submit your application in the early morning and pay an additional fee of 4000 yens. China Embassy in Japan doesn't provide mail service for visa application. If it is not covenient for you to go to the embassy in person, just entrust a travel agency to apply for you.