Apply for a visa L to China in Tokyo

Hello
At this moment I stay in Beijing because of a study on a student X type. I go to Japan for a trip of 3 weeks, but need to go back to China (Beijing) for my trip back home (the Netherlands). I need an entry permit L (tourist) and I am staying in Tokyo for a few days. How can I apply for it? By myself at the Chinese Embassy in Tokyo? Or do I have to go to an agency? And if so: which agency?