Yi sat in the temple for three month perfecting his arms for a oncoming threat. It is said that with every punch Yi has throwed sense the earth shacked and air would be felled with the sounds of thunder.

Monks that dedicate them self to the way of the self reform them self to become get stronger spending days making a finger perfected, only to decided that it's not good enough.

Monks of the self quest for immortality by simply never dying, seeing old age as a disease with a cure. The Way of Self monks commonly have a bitter rivalry with Way of the Astral Self monks, Way of the Astral Self believe that the body is a illusion; Way of Self believe on the other hand that the only thing you can know is your body.       

Self Made Man

when you choose this subclass you get advantage on strength saves and can lift double

Take a Hit

at level 3. You catch their swords they catch these hands. You can use Deflect Missiles on melee attacks if the damage is reduced to 0 you disarm the attacker     

perfected arms and legs

at level 3, you take 10 minute or one level of exhaustion and two Ki point gain the following 

• arms: when you roll your Martial Arts die add a Martial Arts (E.g. you make a attack and you hit your Martial Arts Die is 1d4 so you roll 2d4 + mods)
• legs: When you make a melee attack against a creature, you don't provoke opportunity attacks from that creature for the rest of the turn, whether you hit or not.

you lose the effect when you finish a short or long rest  

perfected skin and organs

At level 6, you can spend 20 minute and 4 Ki points to gain the following

• Organs: you are immune to the exhaustion, eat half Rations, and gain 10ft of movement
• skin: you are resistant to nonmagical slashing, piercing, and bludgeoning, and don't suffering from difficult terrain  

perfected blows

at level 11, when you use Flurry of Blows you can make three attacks. you can use Patient Defense as a free action.

acclimated to perfect

You have made your body perfect why mess with it 

At level 17 you can cast perfected arms, legs, skin, and organs without the costs and you no longer age 

 

perfected body

at level 17 you can spend 7 Ki and 30 minute to gain the following

• perfect Barrage. Whenever you use the Extra Attack feature to attack twice, you can instead attack three times.

the effect ends when you finish a short or long rest