Narushige Michishita, a specialist in strategic and defense studies at the National Graduate Institute for Policy Studies, says Kan needs to address the issue of defending Japan.

NPR: Japan's PM Faces Test Over U.S. Base On Okinawa

"Certainly, they are testing us and using the opportunity created by the Chinese diversion, " said Narushige Michishita, a Northeast Asia security expert at Japan's National Graduate Institute for Policy Studies.

WSJ: Japan: Russian Fighter Jets Enter Its Airspace

"Mr. Abe is seen as being a more assertive Japanese leader, but they may wonder what he will do when faced with two such challenges, " said Narushige Michishita, a Northeast Asia security expert at Japan's National Graduate Institute for Policy Studies.

WSJ: Japan: Russian Fighter Jets Enter Its Airspace