two possibilities that i see.
1. this is a legit effort to rid the world of tension on the peninsula, normalize relations with the south and the US, and become a member of the world community. this will be the first step of many and take several years because they will need to reeducate their people that the rest of the world is not filled with pure, unchallenged evil.
2. this is all an elaborate ruse to get the US to leave the peninsula, act like everything's cool with the south, and then bam! suddenly invade the south because they were a wolf in sheep's clothing all along.
i hope it's more like #1 and that #2 doesn't ever happen.