Japan's push for the right to collective self-defence is posing a tricky question to regional powers: whether it is pursuing militarism that would threaten peace, or seeking its suitable security role that would contribute to regional and global stability.
Seoul and Beijing, two major victims of Japan's past imperialism, are wary of any possibility of its military recrudescence, while a financially strained Washington apparently welcomes Tokyo's desire to assume more security responsibilities.
Analysts say Seoul needs to make careful calculations for its long-term interests, particularly when the Sino-US competition over regional preponderance and Sino-Japan territorial spats intensify.
"Whether we oppose it or not, Japan will push for the right based on its strategic considerations," said Kim Heung-kyu, politics and diplomacy professor at Sungshin Women's University.
"While the right has yet to take shape, Seoul needs to carefully watch its developments, refrain from making emotional responses and explore ways to enhance our national strategic interests."
With official support from Washington, its key ally, Tokyo has sought collective self-defence ― the use of force to respond to an attack on its ally, namely the US ― by altering the interpretation of its war-renouncing constitution or rewriting it.
Japan cited increasing security threats from China and North Korea to justify its pursuit of the contentious right.
But its moves toward rearmament have unnerved South Korea and China, which have long been frustrated by its failure to fully atone for its wartime atrocities including forcing Asian women into sexual servitude during World War II.
Their long-simmering territorial rows have also deepened their distrust toward Japan's push for a "normal" state with a full-fledged military.
Mindful of the deteriorating public sentiment against Japan, Seoul has recently made clear that should Japan want to exercise the controversial right to defend its ally in a peninsular conflict, it must first secure Korea's consent.
Concerns here are that Japanese troops, which colonised Korea from 1910-45, would set foot on the peninsula again on the pretext of defending the US if its ally is attacked by North Korea.
But some experts point out that Seoul should also consider the practical security aspect that the US-Japanese alliance has been one critical pillar of peninsular defence along with South Korea's self-defence and the Seoul-Washington security alliance.
Japan hosts key strategic UN rear bases including Camp Zama near Tokyo, Kadena Air Base and Yokosuka Naval Base, which are to offer logistical support to US forces in case of an armed conflict on the peninsula.
The US and Japan are known to have in place "Operational Plan 5055," a war scenario under which Japan's Self-Defence Forces offer wartime assistance to US troops operating on the peninsula.