This is illegal, that is, it is not protected by Japanese law.

This is when I came to Japan four years ago. At that time, the teacher of the school clearly told us that we could not do remittance, collection, transfer and other activities instead of others. So the "private organization" you mentioned is actually illegal in itself.

If you really want to send money to your sister, the best way (in my experience) is to apply for a savings card of UnionPay in China. There is no handling fee for withdrawing money from Japan Post's atm (different banks charge different fees, but now there seems to be a change in China. For example, my Huaxia Bank seems to have changed from not charging the first fee every day to charging the first fee every month and then collecting it 12 yuan). I don't know.

What I said above is the safest way.

Back to your question, you are passive. First of all, there is no binding force between you and this so-called "personal organization". Even if there is, it is difficult to recognize it in Japanese law. As for the situation that you reported an error to freeze the cash flow of the other account, I have never encountered it. I can't give you a definite answer, but Japan will remind you to confirm your account information many times during the remittance process.

In short, if your situation really goes wrong, you and your sister will be in a very unfavorable situation.

If this goes well, I hope you can use my method instead.