The Korean Studios, handle a lot of out-sourcing from Japan too.
The concept design and game bible are developed in house and then production is farmed out to korean studios.
There was a similar model with tv animation in the 80’s and 90’s, you will see a lot of Korean and Japanese surnames on kids tv shows. But their indigenous games market is very strong too. They have a large young population absolutely addicted to online games. The internet cafe games culture is popular.