Summary
If you make 388,700,000 원 a year living in South Korea, you will be taxed 146,142,569 원. That means that your net pay will be 242,557,431 원 per year, or 20,213,119 원 per month. Your average tax rate is 37.6% and your marginal tax rate is 45.8%. This marginal tax rate means that your immediate additional income will be taxed at this rate. For instance, an increase of 100 원 in your salary will be taxed 45.83 원, hence, your net pay will only increase by 54.17 원.
Bonus Example
A 1,000 원 bonus will generate an extra 542 원 of net incomes. A 5,000 원 bonus will generate an extra 2,709 원 of net incomes.