You Do Need power plug adapter while traveling from Liechtenstein to South Korea.

Here is Why You Need An Adapter

The outlet and plug type used in South Korea is F and in Liechtenstein are C and J. This is how they look like.

Liechtenstein

In Liechtenstein, outlets of type C and J are in use.

Type C

Type J

South Korea

In South Korea, outlets of type F are in use.

Type F