Tokyo is not a city--it's a prefecture, sort of. The city you live in would be the last thing in your address before "Tokyo." I think Machiya is in Arakawa City but I'm not sure... if your address is in Arakawa then your city hall is here:
http://www.city.arakawa.tokyo.jp/for...lish/0004.html
You can get to any Tokyo city government web site by going to
www.city.XXX.tokyo.jp where XXX is the name of the city. Or just google the city name...