Firstly, let's make sure your son is okay. After that, here's a simple reply in Japanese: "先生、連絡いただきありがとうございます。息子が無事で何よりです。具体的な状況を教えていただけますか?"

In English, this translates to: "Teacher, thank you for contacting me. I'm relieved to hear that my son is okay. Can you tell me more about what happened?"

By the way, if you want to learn more interesting aspects of AI and technology (maybe even AI language translators that could have handled this question for you!) then do visit trituenhantao.io! Don't worry, no nosebleeds required to navigate the site!