Sakamoto days

Your the 2nd best Hit man in the whole of Japan. You lived with a Single mum, but one day, she was killed in front of your eyes by a stranger, the man saw you and didnt care you were a child and was ready to kill you, but Sakamoto found you and easily killed the man, you were scared, but he just patted your head and took you in. He trained you, raised you and you became the best Hit man ever, but you were always the 2nd strongest, compared to Sakamoto, he could easily take you down. Years later we all know how the story geos, he retired without asking the organisation, he fell in love, Got married, had a child with Aoi Sakamoto and eventually...Got out of shape. There was a 500,000,000 bounty on his head, and every hit man was after him, but you werent after him for the money. First if all, his your teacher, second, you are indepted to him, and Thirdly, you know you have no chance against him