Kensei
Monks of the Way of Kensei train relentlessly with their weapons, to the point that the weapon becomes like an extension of the body. A kensei sees a weapon in much the same way a painter regards a brush or a writer sees parchment, ink, and quill. A sword or bow is a tool used to express the beauty and elegance of the martial arts. That such mastery makes a kensei a peerless warrior is but a side effect of intense devotion, practice, and study.
Path of the Kensei
At 3rd level, you gain proficiency with three types of martial weapons of your choice, making them into your Kensei weapons. When you wield one of Kensei weapons, you can use it as if it were a simple weapon for your Martial Arts feature.
Additionally, whenever you make an attack with your Kensei weapon on your turn, you gain a +2 to your AC until the start of your next turn while you are not incapacitated and the weapon is in your hand.
One With the Blade
At 6th level, you have honed your skill with your blade. You gain the following benefits:
Magic Weapons. Attacks with your Kensei weapons count as magical for the purposes of overcoming resistances.
Precise Strikes. As a bonus action, you can expend 2 discipline points to mark a creature within 30 feet of you. For 1 minute, you can add double your proficiency bonus to attack rolls against that creature that you make with your Kensei weapons, instead of just normally adding your proficiency bonus once. You can only have one creature marked with this ability at once, if you mark a new creature while this ability is still activated on a different creature, it ends on the old creature.
Sharpened Blade. As a bonus action, you can expend up to 3 discipline points to sharpen the blade of one of your Kensei weapons. Attacks made with the sharpened weapon deal additional damage equal to the number of discipline points spent when you activated this ability. This bonus lasts on your weapon for 1 minute.
Unerring Accuracy
At 11th level you can activate Precise Strikes and Sharpened Blade with the same bonus action on your turn. Additionally, you gain the following benefits when activating those features:
Precise Strikes. Once per turn, if you miss an attack with your Kensei weapon, you may reroll it. You must take the new roll.
Sharpened Blade. Your crit range with the sharpened weapon is 19-20.
Additionally, Precise Strikes now only costs 1 discipline point, and the extra damage from Sharpened Blade is equal to double the amount of discipline points spent, maximum of +4 damage.
Master of the Blade
At 17th level, you have mastered the blade. When you use Flurry of Blows, you can make the attacks with one of your Kensei weapons.