How can I get a lot of paid vacation in Japan? I think foreigners have such troubles as well.
First of all, in terms of the number of days granted by law, the minimum number of days granted is usually 10 days after 6 months (with conditions such as commuting rate).
However, this is the minimum limit of the law, and some large Japanese companies give 15 days or 20 days from the beginning. It is also necessary to confirm working conditions before joining the company.
Also, the vacation is valid for two years, so if you can't digest it in the first year, you can carry over the undigested portion to the next year.
Next is how to get permission to use it, although it is good that it was granted. Normally, in Japan, there is a right to change the season, and the employer has the right to change the time（時季変更権） to take leave if it interferes with the work.
Normally, the right to change the season is not activated except in cases where it interferes with a considerable amount of business. So don't be afraid. However, in Japan, if you suddenly want to take a vacation the next day, you may not be allowed.
A good way is to plan ahead a few months in advance and announce it to your boss or members. For example, declare "Next month will be closed for 4 consecutive days!" If you communicate in advance like this, it will be relatively easy to get permission.