China will continue to support North Korea for the same reason it does Russia, Iran and Syria. It chooses to align itself with rogue regimes, revisionist powers and disruptive actors. It sees its interests aligning more with those who try to destabilize global stability rather than those who try to maintain peace. When Beijing no longer supports dangerous actors around the globe, it will no longer support North Korea. That day, however, is far from coming.
In light of Mr. Xi's visit to South Korea, it is incumbent on Washington and Tokyo to deepen their own relations with Seoul. That has been particularly difficult for Japan of late. But both President Barack Obama and Prime Minister Shinzo Abe should be stressing the future of relations, not just the past.