Is 4 days enough time to get a Chinese visa in Tokyo as a tourist?

Usually, four working days are enough for getting a new Tourist L, so I think you can get one before you go to China.

Since you are not a resident in Japan, you need to apply in person at the embassy. Your valid passport, an application form, a recent taken photo, your hotel bookings, round trip tickets, and your entry permit to Japan are needed for the application.