Find the most populous city in South Korea.
Seoul is the most populous city in South Korea, with a population of over 9.7 million people (as of 2021).
Complete the following task based on the instruction and optional input provided.### Instruction:
Find the most populous city in South Korea.

### Output:
Seoul is the most populous city in South Korea, with a population of over 9.7 million people (as of 2021).