Not so sure that ‘reunification’ is the right way to go.
Keeping them as separate entities would suit me better.
IF they try unification, then N Korean plotters could take over all the defenses South Korea has built up.
The North wants to rule. The South wants to rule. Reunification would work if neither rules. Let Japan administer Korea, they had experience doing so for half a century. (Ducking before the bricks get thrown...)