The son, dubbed North Korea's "Great Successor," stood with his head bowed and somber in a dark overcoat on a balcony at the Grand People's Study House overlooking Kim Il-sung Square and watched the memorial that doubled as a show of support for his burgeoning role as leader.
The unequivocal public backing for Kim Jong-un at his father's memorial provides a strong signal that government and military officials have unified around him in the wake of Kim Jong-il's death Dec. 17.
As he stood overlooking a sea of humanity gathered below him in Pyongyang's main square, Kim Jong-un was flanked by top party and military officials, including Kim Jong-il's younger sister, Kim Kyong Hui, and her husband Jang Song Thaek, who are expected to serve as mentors of their young nephew.
"The father's plan is being implemented," Ralph Cossa, president of Pacific Forum CSIS, a Hawaii-based think tank, said of the transfer of power. "All of these guys have a vested interest in the system and a vested interest in demonstrating stability. The last thing they want to do is create havoc."
Given Kim Jong-un's inexperience and age – he is in his late 20s – there are questions outside North Korea about whether he is equipped to lead a nation engaged in long-stalled negotiations over its nuclear program and grappling with decades of economic hardship and chronic food shortages.
But support among North Korea's power brokers was clear at the memorial service, which was attended by hundreds of thousands of people filling Kim Il Sung Square and other plazas in central Pyongyang.
"The fact that he completely resolved the succession matter is Great Comrade Kim Jong-il's most noble achievement," Kim Yong Nam, president of the Presidium of the Supreme People's Assembly, told the massive audience at the square.
"Respected Comrade Kim Jong-un is our party, military and country's supreme leader who inherits great comrade Kim Jong-il's ideology, leadership, character, virtues, grit and courage," said Kim, considered North Korea's ceremonial head of state.
Life in the North Korean capital came to a standstill as mourners dressed in thick, dark colored jackets blanketed the plaza from the Grand People's Study House to the Taedong River for the second day of funeral ceremonies for the late leader. A giant red placard hanging on the front of a building facing Kim Il Sung Square urged the country to rally around Kim Jong-un.
Kim Jong-il, who led his 24 million people with absolute power for 17 years, died Dec. 17, according to state media. He inherited power from his father, North Korea founder Kim Il-sung, who died in 1994, in what was the communist world's first hereditary succession.
Attention turned to Kim Jong-un after he was revealed last year as his father's choice among three known sons to carry the Kim dynasty into a third generation.
The process to groom him was rushed compared with the 20 years Kim Jong-il had to prepare to take over from his father, and relied heavily on the Kim family bloodline and legacy as guerrilla fighters and the nation's founders.
Kim Il-sung is North Korea's first and only president; he retains the title "Eternal President" even after his death.
Kim Jong-il held three main positions: chairman of the National Defense Commission, general secretary of the Workers' Party, and supreme commander of the Korean People's Army.
According to the constitution, his position as chairman of the National Defense Commission makes him "supreme leader" of North Korea.
Kim Jong-un was made a four-star general last year and appointed a vice chairman of the Central Military Commission of the Workers' Party. Since his father's death, state media have bestowed on him a series of new titles signaling that his succession campaign was gaining momentum: Great Successor, Supreme Leader and Sagacious Leader.
"Kim Jong-il laid a red silk carpet, and Kim Jong-un only needs to walk on it," Jeung said.
Last weekend, the Workers' Party newspaper, Rodong Sinmun, called on the younger Kim to step into his father's role as supreme commander of the armed forces.
He may be officially named supreme commander of the military ahead of Jan. 8, which is believed to be his birthday, said Cheong Seong-chang at the Sejong Institute in South Korea.
The aftermath of Kim Jong-il's death has been watched closely for clues about who in the military and Workers' Party will form Kim's inner circle of trusted aides during the sensitive transition to leadership.
Following right behind Kim during a Wednesday funeral procession through Pyongyang streets with Kim Jong-il's hearse was his uncle, Jang Song Thaek, who is a vice chairman of the powerful National Defense Commission and has family ties to the military.
For Thursday's memorial, North Koreans packed the main square as well as the plaza in front of a Workers' Party monument of a hammer, sickle and writing brush.
Flags at half-staff fluttered in the wind on the cold winter's day, and people were bundled up in parkas. State TV showed a delegation of foreigners attending the memorial.
They bowed their heads as eight artillery guns fired; military officers removed their hats while the booms resonated across Kim Il Sung Square.
The streets went still again for a three-minute period of silence. Heads bowed, workers paused next to a green train and bystanders stopped where they were, some standing next to their bicycles, as trains and boats sirens blew their horns, according to state media.