Summary
If you make 100,100,004 원 a year living in South Korea, you will be taxed 22,444,829 원. That means that your net pay will be 77,655,175 원 per year, or 6,471,265 원 per month. Your average tax rate is 22.4% and your marginal tax rate is 29.0%. 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 29 원, hence, your net pay will only increase by 71 원.
Bonus Example
A 1,000 원 bonus will generate an extra 710 원 of net incomes. A 5,000 원 bonus will generate an extra 3,550 원 of net incomes.