Santoryu Style

Santoryu is a style of sword fighting where the practitioner wields three Katana; one in each hand and one in the mouth.There are many different techniques for this sword style, including high speed attacks ("Shishi Sonson"), direct hit attacks ("Oni Giri") and compressed air projectile attacks ("Hyaku Hachi Pound Ho")

Katana Style Santoryu

Starting at 3rd level, you gain the ability to wield three swords at once in combat, wielding both with your hands and one in your mouth. You can draw or stow three weapons when you would be able to draw or stow only one, and you can engage in two-weapon fighting with longswords or katanas. A Santoryu Master uses his dexterity modifier in place of his strength modifier on attack rolls.

In addition, when you are engaged in two-weapon fighting, if you hit a creature with both your attack made as part of an Attack action and the bonus action attack, you can make a third attack using a sword in your mouth as a reaction.

Busoshoku Haki

At 3rd level, by power of your haki, while not wearing armor or shield your AC equals 10 + your Dexterity modifier + your Wisdom modifier

Armament Haki

At 7th level, you can imbue your attack with Armament Haki for one turn as a free action, adding 1d6 to damage force damage to all attacks made this turn. this damage increases to a 1d8 at 10th level and 2d8 at level 15.

You can also use your Armament Haki as apart of the same action to bolster your own defense. Until the start of your next turn, you gain resistance to a damage type of your choice (except psychic damage).

You can use the features above a total of times equal to your proficiency bonus, regaining all uses after finishing a long rest

Kenbunshoku Haki

 At 7th level, your haki allow you short glimpses into the future. You gain a bonus of +5 to your passive Wisdom (Perception).

In addition, you add your Wisdom modifier to your Initiative rolls and Dexterity saving throws.

Finally you can use you blade to parry an attack as a reaction by subtracting your Dexterity modifier from rolled attacks possibly causing it to miss. 

Nigorizake

Starting at 10th level, your intensity in battle can shield you and help you strike true. When you use your Action Surge, you have advantage on all attacks made as part of that surge against a creature you have hit on this turn.

Tatsu Maki Santoryu

At 15th level, your melee attacks have reached a point where they can slice through and create wind. You can forgo any attack you can make with a sword by a ranged weapon attack against a creature within 30 feet, that causes the same damage of your attack using that weapon. If the weapon is magical, the damage of this attack also is.

in addition when you score a critical you can recharge one of the Armament Haki usages.

Kiki Kyuutouryuu Ashura

At 18th level, as a bonus action, you can create an illusion that resembles a six-armed demon. The illusion lasts for 1 minute, or until you end it early as a bonus action. For the duration, you can make an additional attack, instead of one, as part of your bonus action when you are engaged in two-weapon fighting, and you score critical hits on a roll of 18-20 with your attacks.

you can use this feature up to half your proficiency bonus, after that you can't use it again until you finish a short or a long rest.

whenever you score a critical hit on an attack with you swords the target additionally suffers half of the damage from the attack at the end of its next turn.

Finally, you can use the sword in your mouth defensively to assist with parrying attacks. your gain a bonus of +2 to your AC against weapon attacks, while you are not wearing armor or using a shield.