An era is ending, though many are in denial and floundering over the next steps. North Korean leader Kim Jong-un appears to have chosen a path that will end meaningful denuclearization diplomacy with the United States for the foreseeable future and usher in a new chapter in the North Korea saga: living with a nuclear North Korea. This raises the stakes on a longstanding challenge: how the US, South Korea, and Japan can best work together to contain and constrain a permanent and growing North Korean nuclear threat to peace and stability in Northeast Asia. The three countries will also need some modicum of consensus with China and Russia to forge this cooperation under very adverse circumstances.