Visit Shanghai, being Italian student resident in Tokyo

Since you need to have a single entry Tourist type, you need to prepare your hotel bookings, round trip tickets, your valid passport, an application form, a recent taken photo and your resident permit.

For your situation, you may need to apply through a local agency for application. The application fee is 4000 Yen for a single entry one. The tour agency may charge some service fee, so you may need to cosult the different tour agency for detail prices.

I am visiting a friend, so I haven't reserved a hotel. Plus, is the travel agency necessary? Thank you!

If so, you can ask your friend to write you an invitation letter, so that the hotel bookings are not necessary.

Based on my information, the agency is necessary since you have a resident permit to live in Japan. If you still concern, you can try to consult the embassy directly for an exact answer.