Article has such scant information, no mention of what type of missile.
I know they're probably referring to the Type 12 which is a surface to surface cruise missile, and they eventually want to integrate that to launch from F-15J and also introduce a ship launch version. 1000 of these in the Ryukus with extended range are a major threat vector to consider.
Anyway, Japan is doing their own version of "Salami slicing" but against their own constitution. They made a lot of noise about DF-11s and -15s falling in their EEZ when the PLA shot them over Taiwan. Best for China to assume Japan will fight for Taiwan in the event AR occurs, after all an "emergency for Taiwan is an emergency for Japan".