Dear mother,
I am Ken. I'm writing this letter just to let you know that I will take care of Mai as best as I can. As a parent, I understand that you will be worried whether or not your daughter's boyfriend is a good person or not. But I just want to tell you not to worry because I am trying to be a good boyfriend. Mai is also trying to change to be a better person. Please take care. One day I will visit you and say hi to you.