Send in the Robots

It strikes me that Japan could defend their claims to the Senkaku islands by using CROWS and unmanned radar on the islands themselves supported by armed UAVs patrolling the area.

Remote weapon stations with gatling guns, anti-ship missiles, and air defense missiles would be able to shoot at landing attempts and Chinese aircraft in the region. UAVs would provide a mobile force to scout and shoot. They would be the reserve force to reinforce posts under attack.

All would be under the control of human operators--perhaps even the Japanese coast guard to keep a lower profile.

Smart mines seeded aroung the area would be a good idea, too.

Consider it a sea version of this.

In theory, it isn't as provocative as putting troops on the islands. And it has the advantage of not risking Japanese lives in defense of the rocks for low level threats. That could make it easier to sell at home.