I’m a bit skeptical that what’s in this report indicates to the possibility of China attacking Japan. What use are multi-mile long columns of tanks and artillery in what would be a purely naval conflict? You aren’t going to land those sorts of forces on the miserable little rocks that are the Senkakus.
I don't know what China has in mind, but it wouldn't take much to land a battalion of Chinese marines. I think some aircraft from the mainland have the combat radius to reach the islands. Chinese subs and surface ships could form a cordon around the landing force. I don't know if there is enough flat land to build an airstrip, maybe that's what all the "survey ships" are doing there. Land the marines, build a strip, base some fighters, and its all over.
The question is, what will the US do. The US is treaty bound to support the Japanese claim on these islands, not that that means anything. So far, all Obama has done is to park the carriers in their home ports for "budgetary reasons".