North Korean state media have swaddled Mr. Kim’s childhood with mythmaking, portraying him as an excellent marksman and a “genius among geniuses” who loved to drive fast cars. At age 16, he is said to have written a research paper analyzing his grandfather’s leadership during the Korean War.
From 1996 until at least 2000, Mr. Kim is believed to have studied in public schools in Switzerland disguised as the son of a North Korean diplomat. The classes were taught in German, and Mr. Kim struggled with the language. A video recorded at the time shows him uncomfortably tapping a tambourine in a music class.
“We weren’t the dimmest kids in class but neither were we the cleverest,” a classmate, Joao Micaelo, told a British tabloid in 2011.
Mr. Micaelo and others have said Mr. Kim was a quiet teenager who loved James Bond films and playing basketball. But he stood out because he had expensive sneakers and gadgets, including a Sony PlayStation, and enjoyed the services of a cook, a driver and a private tutor.
One classmate, Marco Imhof, recalled how he once scolded a servant for serving cold spaghetti. “I was surprised because it was not how he normally was,” Mr. Imhof said in an interview published in 2010.
There is evidence that Mr. Kim’s time as a youth in Europe, and perhaps other countries, left an impression. In his memoir, Mr. Fujimoto recalled conversations with Mr. Kim as a teenager in which the future leader expressed frustration with power shortages at home and marveled at overseas department stores.
“Japan was defeated by America, but they’ve greatly reconstructed the country. The shops were full of goods. What about our country?” Mr. Fujimoto quoted the young Mr. Kim as saying. Later in the conversation, Mr. Kim suggested that North Korea should learn from China’s market-oriented economic policies, Mr. Fujimoto wrote.
Such accounts have left some analysts hopeful.
“When the time comes, Kim Jong-un is expected to adopt policies that will ease his country’s isolation and embrace good things from the West,” Paik Hak-soon, a North Korea expert at the Sejong Institute, a think tank outside Seoul, said in a paper on Mr. Kim’s leadership published in February.