I think that its wiser to choose Japanese, coz this country supports new technologies, including cryptocurrency, way stronger than China. But since I dont know your purpose to learn new language, my advice may be wrong for you.
If you are fond of travelling in different countries of the world and that you dont know different languages, then it is better to learn the languages which are mostly spoken in the entire world. Learning of English, Chinese, French and Japanese can help you in much better way as it will then help you in communicating with more people around the globe. Learn the language which attracts you the most.
Yeah I agree that it's best to learn the language that you love the most and feel comfortable with it. I know this may seem subjective but I recommend learning Japanese since it's not only pleasing to hear but it's also the language of one of the most developed countries in the world. Moreover, it's widely believed that the inventor of bitcoin came from Japan, so with bitcoin-influenced mind, I think it will be an advantage to study Japanese.