Applying for visa via travel agency

Hello,
I'm a Swedish University student currently studying in Japan for a year. I plan to visit Shanghai for about a week next month and I have some questions regarding the application through travel agencies.
As far as I understand there's no other way to apply as a foreigner currently living in Japan. But I wonder, does this mean I have to buy one of the trips they have to offer at the agency or can I bring the flight ticket and hotel information that I booked by myself?

Thank you.