South Korea Vows To Target Kim Jong-un If Attacked By North Korean Nuclear Weapons

I would think a lot more than targeting regime leadership and key sites would happen to North Korea if they used a nuclear weapon against the South:

South Korea vowed on Friday to counterattack North Korea’s leadership including ruler Kim Jong-un if Pyongyang uses its nuclear weapon.

“If the North harms us with nuclear arms we will directly target, punish and retaliate against the North Korean leadership, including its war command,” said Lieutenant General Lim Ho-young, strategy and planning director of the Joint Chiefs of Staff. “We will operate our strike capabilities, including missiles that are capable of making precise strikes en masse simultaneously and will deploy our elite special operations forces.”

The retaliation will target the North’s command and control system, he said, as well as missile facilities and submarine bases using the South’s capabilities. He said the South has missile capabilities comparable to cruise and ballistic missiles of the North, while its air-to-ground guided bombs and missiles are superior to those of the North.  [Joong Ang Ilbo]

You can read the rest at the link, but if the North launched a nuke at Seoul you would think the US would respond in kind against South Korea.