At the time this universe was set, in early 2030s to mid 2040s, the Korean Peninsula had long been united with the South Korea annexed the North in a relatively short but brutal full scale war called the Reunification War in both North and South Korea, in 2027.

After the Chinese gave their support to South Korea annexing the northern part to form an United Korean Republic, in return of a demilitarized zone in the 40th Parallel north, as a buffer zone for the two states, immediate withdrawal of US forces from Korea along with an extension for Chinese high-speed rail line (CRH) to Seoul in the spirit of Belt and Road Initiative in return of Korean counterpart, the KTX, opened it's own service to Harbin and Yanji, the latter have a significant number of Koreans lived in the area, the South Koreans, by now simply called Koreans began to rebuild the devastated northern part of the peninsula, almost in a repeat from the first phase of the Korean War in 1950-1953 with the area lost almost 30% of it's military-age population, not counting those who were publicly executed by the South Koreans with machine guns, with unprecedented leeway from the Americans, or fled to China and never return.

When the South Korean military captured Pyongyang after bloody combat a week after the North Korean invasion were repulsed, the world was captivated with the memories from the Iraq War as statues of Kim Il-Sung and Kim Jong-il at Mansu Hill Grand Monument were publicly torn down. Meanwhile in the northeast of Pyongyang, the Kumsusan Palace of the Sun was ransacked and the embalmed body of both Kims were removed from its pedestals and brought into Kim-il Sung Square, subsequently renamed the Jayu (Liberty) Square, when it were hung, along with Jong Un's one upside down with meat hooks, but not after South Korean soldiers and angry Pyongyang citizens pelted the bodies with rocks and rotten foods, spat in, shot in, bayoneted, and kicked until its features were barely recognizable, before the former leaders' body were brought into one of the city's remaining functional crematorium to be cremated and their ashes scattered into the wind by a South Korean helicopter.

South Korean special forces were also dispatched to hunt down any Kim family left alive in the peninsula.

The reintegration policy by the newly unified Korea under conservative President Seo Go-Hyun is considered as harsh, with existing ban on communist symbolism and propaganda was extended to North Korea while the government paid and employed North Korean POWs and refugees to reconstruct the country as a whole, further with aid of Japan the its Western Allies but also China in some degree. while administratively the former North Korean territory was administered as an autonomous entity under UKR, the Koryo Special Administrative Region, unlike Hong Kong and Macau, it's not "one country, two systems"

While most North Koreans, especially outside Pyongyang, welcomed the South Koreans as liberators, others; angry, disenfranchised and extremely loyal to the old regime, launched insurgency against the new authority with bombings, assassinations, and sabotage as well as show of force protests under the flag of New Korean Revolutionary Army, allegedly supported by China in some degree. Despite the insurgency in the mountains, the reconstruction proceeded, with notable projects as Reunification Memorial Park, the transformation of the old Korean DMZ into nature preserves, and New Pyongyang.

The "New Pyongyang" project involves the redistribution of former DPRK high official apartments to former political prisoners of the Stalinist Kim regime along with the expansion of the city, with the project was symbolically started by the demolition of the Juche Tower with explosives. The projects was allowed by the massive investments in real estate, mining, agriculture, and fisheries by southern Korean businesses along with Japan, Australia, United States, European countries, but also China and even Indonesia. Other than reconstruction of cities, in the first year of the reunified Korea, the Northern infrastructure were upgraded and rebuild as well; a new solar field built by a South Korean and Japanese consortium along with transformation of former Yongbyong nuclear facility into a fusion power plant, the first in the peninsula; the Chinese reconstruct former North Korean gravity dams in Yalu River, Unbong, Wiwon, Supung, and Taipingwan; the Americans rebuild and upgraded Ponghwa Chemical Complex in Sinuiju while the Russians reconstructed the Sungri Refinery.

The rapid rebuilding increased Korea's prosperity. Physically, North Korean cities is almost as developed as it's Southern counterpart in 2040s, while generational divide take longer to dissipate, and such concern is the raison d'etre for the separate administration in the territory with the former Committee of Five Northern Korean Provinces as the basis for the Koryo SAR government while the lead coordinating agency for the international reconstruction effort was the Ministry of Unification.

Only the United Korean armed forces stationed on the Koryo SAR territory, as the Treaty of Panmunjeom barred any foreign military being stationed or deployed in the area with exception of exercises, and in return of American withdrawal the Koreans were permitted to expand "without any external limitations" including by developing it's own version of Terminal High Altitude Area Defense missile defense systems, rendering the country as the most militarized one in the democratic Asian world as well as maintaining a conscript force. To further "remind" the Chinese the Korean government created a Visiting Forces Agreement to regulate American access to Korean military infrastructure in the southern part of the peninsula and later became one of the founding members of the Pan-Pacific Defense Union (PPDU).