Since May, North Korea has several rounds of short-range ballistic missiles, and apparently Japan failed to detect their exact trajectories more than two of those times.
Citing several anonymous sources, Tokyo-based Kyodo News Agency said the missiles launched in May and September, in particular, were not accurately tracked by either Japan's Aegis-equipped destroyer in the East Sea or its Air Self-Defense Force radar systems.
Kyodo News said it was harder to get accurate readings because the missiles were flying at lower altitudes with more complicated flight paths.
It's easier, it said, to track them from South Korea because it's closer to the launch site, acknowledging the negative impact of Seoul recently terminatiing its military intel-sharing pact with Tokyo.
Kyodo also said Japan needs to strengthen its cooperation with South Korea and the U.S.