Summary
If you make 13,844,480 円 a year living in Japan, you will be taxed 4,048,786 円. That means that your net pay will be 9,795,694 円 per year, or 816,308 円 per month. Your average tax rate is 29.2% and your marginal tax rate is 37.2%. This marginal tax rate means that your immediate additional income will be taxed at this rate. For instance, an increase of 100 円 in your salary will be taxed 37.16 円, hence, your net pay will only increase by 62.84 円.
Bonus Example
A 1,000 円 bonus will generate an extra 628 円 of net incomes. A 5,000 円 bonus will generate an extra 3,142 円 of net incomes.