South Korea, officially the Republic of Korea, is a country in eastern Asia.
U-GIN Genetic Research Facility
Ultron and the Maximoff twins later arrived in Seoul, South Korea where he arrived at the lab of U-GIN Genetic Research Facility and confronted the Avengers' ally Doctor Helen Cho. Ultron informed her that he intended to use the Regeneration Cradle to create the perfect, synthetic, humanoid body for Ultron, made from Vibranium. When Cho resisted Ultron used the Scepter to take over control of her mind and force her to do his bidding.
As the synthetic body was built inside the Regeneration Cradle, and was given a Vibranium composition on Ultron's request, thus making it more durable, Ultron revealed to the Maximoff twins the power contained inside the Scepter: an Infinity Stone, with which Ultron would integrate with his new synthetic body and adopt god-like powers. Cho then plugged Ultron into the machine to upload his base consciousness into the being. When Wanda Maximoff attempted to read Ultron's mind through the synthetic body, the being allowed her to discover that Ultron's actual plan was to cause a global catastrophe that would usher in a new age of Earth's evolution.
Ultron attempted to defend his actions, noting that there was no room for the weak in the world, however, doubting Ultron's cause, Wanda removed Ultron's mind-control over Helen Cho in secret to allow her to sabotage the upload. Ultron sensed that the Avengers had arrived in Seoul to stop his plans and ordered his soldiers to evacuate. However Cho used the opportunity to stop the upload, in response Ultron fired a blast of energy at her which stunned her, in the chaos the Maximoffs escaped and Ultron was left with no choice but to move the Regeneration Cradle onto a truck and escape.
Hawkeye managed to locate Ultron in a U-GIN Truck in Seoul. Hawkeye suggested shooting it, but Captain America pointed out the possibility that the Infinity Stone inside Ultron's synthetic body could destroy the city. Rogers jumped on the truck, interrupting Ultron's download. Rogers decided to keep Ultron busy so that Hawkeye and Black Widow could retrieve the body. Rogers and Ultron fought, with Rogers doing his best to hold his own. Rogers lost his shield. Following the battle onboard a motorcycle, Black Widow was able to retrieve it for him. The fight eventually spilled into a moving train.
Meanwhile, Romanoff entered the truck; however, the Ultron Sentries lifted the truck into the air. On the train, Ultron almost defeated Rogers when Scarlet Witch and Quicksilver came to Rogers' aid. Ultron begged the twins not to turn against him, but Scarlet Witch pointed out that they had no choice. Ultron killed the conductor of the train and fled. This caused the train to speed out of control. Rogers had Quicksilver move civilians out of the way while Scarlet Witch used her powers to successfully stop the train. Romanoff managed to roll the Regeneration Cradle into the Quinjet in midair, but she was kidnapped by Ultron in the process.
Seoul was among the cities noted by WHiH News anchor Christine Everhart to be still "on the mend" as a result of the incidents involving the Avengers, in part due to their tactical response, as late as May 3, 2016 when the issue of the Avengers' management and responsibility was being discussed.
Black Panther learned that weapons dealer Ulysses Klaue planned to sell a stolen Vibranium artifact in Busan. Therefore, Black Panther took Okoye and Nakia with him to Busan in order to arrest Klaue. They entered Jagalchi Market Casino and waited for Klaue to come. However, Black Panther recognized Everett Ross among the customers and identified him as Klaue's buyer.
Klaue eventually arrived in the casino and met with Ross. As the transaction was being made, Okoye was recognized as a hostile by Klaue's bodyguards. A shootout erupted in the casino and although Black Panther, Nakia and Okoye defeated several bodyguards, Klaue managed to escape in a column of SUVs. Nakia and Okoye took their car to chase him, leaving Black Panther behind to catch up with them thanks to Shuri.
A hot pursuit engaged in the streets of Busan. After they damaged most of Klaue's SUVs, Klaue destroyed Okoye's and Nakia's car, leaving only Black Panther to chase Klaue. Klaue destroyed the car Shuri was remotely controlling, but Black Panther used the kinetic energy absorption of his suit to destroy Klaue's car. Klaue's was then stripped of his prosthetic arm and delivered to the CIA, to be taken to the CIA South Korean Black Site.
In the CIA site, Ross interrogated Klaue, who revealed the true nature of Wakanda, a rich African country heavily relying on Vibranium. However, while Ross confronted Black Panther about the matter, Erik Killmonger blew a hole in the wall to rescue Klaue. Another gunfight erupted, in which Ross was heavily injured while Black Panther failed to stop Killmonger and Klaue. Facing this defeat, Black Panther, Okoye and Nakia left Busan with Ross.