This character's name is Yin. I'm still working on a story, for now, he is a man who has left a violent past behind him, having served as chief assassin for a powerful warlord over thirty years ago.
Living alone far from his previous employer's domain, he survives as a farmer.
One day, Yin hears an explosion not far from his house and upon investigating where the explosion originated he finds a child who is Boa.
The image below is of Boa 15 years after Yin found him.