Traveling from US to Shanghai for 2 days on business, then to Japan for 2 days, and back to US

I am US citizen. Do I need visa or am I qualified for 144 hours twov? Some travel agent said I am not qualified because the purpose of the trip is for business. I will be in Shanghai for 2 days but will stay at the hotel in Shanghai (will be out of the airport/won't be at the airport for 2 days!!).