Back Blade

Backblade.

Anime about a swordsman who only uses the back of an extremely sharp sword. Sword can cut through anything but still he uses the 

back to where it is just dull and no sharpness. Instead of killing, the has them all to submit and fall under where ever he decides they should go.... if he wins he is able to instruct them to turn selves in or kill themselves as he would not have blood on his hands.

He eventually gets an apprentice. A young girl and she is given a regular sharp blade for she will inherit his when he dies... when he decides she is ready... he will take his own life... this makes her not want to train because she loves her sensei but he motivates her that the world needs her more than it needs him and she will surpass him. She cries in him telling her both these things and begins working hard for him everyday so she can become not like him, but her own person to who will be stronger than he is. Even to do the needed of season 5 when she has to defeat she shadowself that everyone has... as she has to overcome the ideals instilled by her master to not kill to kill this shadow that had solidified itself in human flesh...