Summary
If you make 102,700,000 원 a year living in South Korea, you will be taxed 23,198,757 원. That means that your net pay will be 79,501,243 원 per year, or 6,625,104 원 per month. Your average tax rate is 22.6% 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.