Though I decided against making a yakuza class – i think the basic rouge covers this well enough – the kensai is unique enough to have its own archetype in Oriental Adventures. You can find other classes for OA here.
Kensai means “sword saint” or “sword master” and is usually applied to characters who have perfected the art of fighting with the sword – in particular a katana. In the Oriental Adventures setting this is broadened to include almost any type of weapon. Thus, there may be kensai who use halberds, kensai who use swords, etc. The player is allowed to choose the kensai character’s special weapon (referred to hereafter as the specialised weapon). In all cases, it is the kensai’s aim to become the perfect master of his weapon. For the man and weapon to become one, acting on a single thought, is the ultimate goal of a kensai.
To achieve this the kensai must master his weapon and himself, and must study and learn other arts. He must practice daily with his weapon, condition his body and purify his spirit through meditation and ordeal. The kensai must be lawful, although he can be good, evil, or neutral.
THE LIFE OF A KENSAI
Because of his dedication to perfecting your combat art, the kensai must follow certain restrictions. You can never use a magical weapon of the type you specializes in, since such a weapon is not a true measure of your skill. All types of armor are prohibited for the same reason.
A kensai must train and practice for at least two hours a day. Any practice over two hours has no additional effect. Ignoring practice has no immediate effect; it comes into play when the character is ready to advance to the next level. Every two hour practice session skipped must be made up before the character can advance. When catching up on missed practice, the character can practice up to four hours per day: two hours for that day’s practice and two hours making up for the missed practice.
Each time a kensai advances a level, there is a percentage chance equal to 10 times his new level that he will be challenged to a duel. The challenger is a kensai of the same level that the character just attained. A duel is a one-on-one fight between two characters. Neither character can receive aid or support from anyone else. Kensai characters cannot use magical weapons or armour in a duel. The duel can be a very formal affair at a pre-arranged site and time, or an impromptu meeting of two characters.
If the character refuses to duel, he forfeits his newly gained level, losing just enough experience points to place him at the bottom of his old level. In addition, he loses honor.
If he accepts the duel and loses, he also loses both honor and his new level, the same as if he had refused the duel. This duel doesn’t need to be fought to the death, however; the duelists can agree on any conditions. Surrender, first blood, or first strike are common ending conditions; even first draw can determine a victor, although this is rare. Note that when the character reaches 10th level, he must fight a duel to advance a level.
A kensai may be challenged to duel an NPC at any time, not just when he advances to a new level. Refusing or losing such a duel costs the kensai honor, but does not cause him to lose a level of experience.
A kensai need not be of high birth as the practices and techniques of the class are available to everyone. However, family and honor are important. Gaining and maintaining honor are a vital part of the kensai’s life; any kensai whose honor falls below his family’s honor loses his status in the class. Thereafter the kensai is treated as a bushi of the same level and advances in level according to the bushi character class. He loses none of the abilities he had as a kensai, but he can never gain new kensai abilities.
Your specialised weapon is the only defence you need and you disdain armour which affects the Wa – harmony – between you and your katana. Beginning at 3rd level you lose all armour and shield proficiencies, however, while you are wearing no armour and not wielding a shield, your AC equals 10 + your Dexterity modifier + your Wisdom modifier.
Beginning at 3rd level you are lighting quick to draw and strike with your specialised weapon. You gain advantage on initiative rolls when using your weapon of choice. Additionally your specialised weapon is considered magical for the purposes of overcoming damage resistance. Finally, you gain iaijutsu focus as a class skill and automatically gain an inspiration when entering in to a psychic duel.
Beginning at 7th leveI, your specialised weapon attacks score a criticaI hit on a roll of 19 or 20. In addition you can add a level appropriate proficiency die to your damage with the specialised weapon (DMG pg. 263) and gain a to-hit bonus equal to half your proficiency modifier (round down, minimum of 1).
At 10th level, once per step of your proficiency modifier you may choose to maximise the damage of your attack with your specialised weapon. You regain uses of this ki power after a long rest.
At 15th level, you become immune to fear and inspire fear in your enemies. Intelligent enemies within 10 feet of you must make a Wisdom saving throw or become frightened. The DC for this save is 8 + proficiency bonus + Strength or Wisdom bonus (your choice).
WHIRLWIND OF BLADES
At 18th level, you gain the ability to make a whirlwind attack. When you use your attack action, you can give up your regular attacks and instead make one melee attack against each opponent within reach. You must make a separate attack roll against each opponent.