Right now is the time to file a tax return. If your status is Business Administration, and you are self-employed, you are required to file this.
However, you must be careful even if your status is, for example, Engineer/Specialist in Humanities/International Services.
If you have a plurality of sources of income, you must file a tax return. You are hired by a Japanese employer, but you might also be hired by an employer of your own country. If you get paid by more than one employer like this, you must file a tax return.
This started on February 16 and lasts till March 16. If you need to file it, please make sure to file on time.