AP Photo

For years, a prime method for decoding the impenetrable North Korean regime has been the Dear Leader's sushi chef, a defector named Kenji Fujimoto. When I met him in Tokyo several years ago, he looked as if he had just stepped off a construction site. His body was squat, his face rough. From his vantage in the kitchen, Fujimoto had been an astute observer of Kim Jong Il's court-and the struggle within that court to win favor.

Years ago, Fujimoto began noticing the growing prominence of Kim Jong Il's youngest son, Kim Jong Un. He had grown close to his father; a special bond had formed. On the surface, Kim Jong Un seemed like a nice boy, dutiful and respectful. Fujimoto, however, sensed these were mere exterior traits. He sensed that Kim Jong Un...