Summary
If you make 13,923,728 円 a year living in Japan, you will be taxed 4,078,230 円. That means that your net pay will be 9,845,498 円 per year, or 820,458 円 per month. Your average tax rate is 29.3% 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.