If the other party doesn't reply, you can send another one. In addition to the general greetings, you should also explain the last email you sent him and ask if you received it. Then, for the sake of confirmation, briefly mention your last content. Finally, please ask him to take some time to answer.
You have no problem expressing yourself in Japanese. I think it is feasible and necessary to follow up the above as an enterprise.
Please refer to it.