You've sworn a vow, even if it's just to yourself, to keep somebody safe. When you choose this you may choose an individual, a group of people, an ideal, or really anything that you swear your life to protect.

You may spend a point of willpower to automatically take the blow for someone else unless the attacker rolls a 19 or a 20. You still roll dodge, if successful you not only take the blow but you block the attack as well.
You receive a +1 bonus to all d20 rolls for every ally that has had their wound points are damaged and is in real danger. You receive an additional point of willpower for every ally that is rendered unconscious, disabled, or dies in your presence. Furthermore, if an ally ever dies in your presence you both your stamina and chakra are completely refilled as long as you spend two points of willpower and at least one action grieving your loss in some dramatic fashion.