They won't be content with an island or two. They are to make the entire sea under their control for their own strategic reasons: securing their own ports and keeping enemies (practically everyone but themselves) out.

Ultimately, their aim is to break the cordon that is formed by Taiwan, Japan, the Philippines, Malaysia, and Indonesia so that they can project power in the Pacific.

Perhaps another goal is to turn us (the island nations I just mentioned) into vassal states (with the exception of Taiwan which they will [re]take outright). That way, they'd have a buffer against anyone who wants to take them on.