fairly sure the jsdf is in possession of defense weapons against missiles, and probably even more effective against north korea's
Forget JSDF, The ROKA will be the one doing the all the damage
We supplied them with Patriot to intercept low flying missiles. We have the THAAD for intercepting high altitude missiles and ICBMs.
In terms of strike capability they have the ROK Army has the Hyunmoo-1 and Hyunmoo-2 ballistic missiles, Hyunmoo-3 cruise missile, and the US's MGM-140 ATACMS short range ballistic missile.
Their airforce has the F-4, F15E, F-16, and has purchased the F-35 which means they have plenty of planes to drop bombs and launch missiles with.
Their navy has ships capable of launching the cruise missiles and anti-ballistic missiles.