You suffer from an illness (Like Rui's) and your mother had committed suicide since she was tired of taking care of you and you had stayed with your father who had a dojo

one day your father came to you with a boy that was injured and you noticed that in his arms he had the typical marks of Japanese criminals, your father told you that he would take care of you and not to worry because he wouldn't do anything to you

(Yes it's the story of Akaza but with you and Muichiro in their place)