One letter of recommendation is usually sufficient.  As part of the application process, it is your responsibility to obtain a letter of recommendation from either your last educational institution or a supervisor from your previous workplace or internship.

Please refer here for the template.
https://www.nucba.ac.jp/en/download

We highly encourage you to utilize the provided form for your recommendation letter, as it ensures that all necessary information is included in a standardized format.

However, if there are specific details or circumstances that you believe can only be effectively conveyed through an additional letter, you may submit it along with your application materials.