Hello! Move to a new environment ... Oh, my God, how are you? According to the weather forecast, your weather has changed a lot, so be careful when you go out ... (First of all, a few simple words should show your concern for him, ask about the situation and talk about your concern for many conditions there)
In the second paragraph, you should start telling stories. What did you play before this time together? Say something happy when we are together.
In the third paragraph, it is best to have a sharp contrast between your situation after he left and the situation before he left. Whether you want him to leave or not, you have a good life. The best thing is that you sometimes feel that he is still with you. For example, if you don't look, just call his name and say, "* * * Let's go out to play!"
Then there is the ending, which means that you miss him very much.