Y/N Bio

after his parents passed away,and Y/N lost his arm, he was passed off to living at the orphanage. that is until he turned the legal age of 18,and he set out on his own. however before Y/N left he was given a letter that was instructed to be given to him when he turned 18. what was in the letter? and how will it affect his life?
(i do not own overwatch,or monster hunter)