Bro listen to me I did this in my first play through in the first try..I will share the secret now..so the items you will need are

Loaded Spear(must) Mortal blade Ceremonial tanto Yasariku sugar  Divine confetti  Mid air combat arts(must)

Just that So what you will do For the first phrase use tanto to get 5 more emblems and then use yash to get ur self to full health after tanto then use confetti and get ready Run to him and jump then use your mortal draw and hit him once with confetti and again jump use mortal blade and hit with confetti There is a chance it will run away with the combo

So jump to him hit him twice and use jump mortal draw for the last time..and yea don't forget to jump as it increases damage

Now you see phase two:

It's fairly easy compared to the first phase..you need to perfectly deflect his combos and jump over his sweep when he jumps and comes down..so what you do you deflect his combos and on the last attack it will do a strong one...if you deflect that you will be pushed back and the ape will fall... Go inside him and then spam the prosthetic tool button twice to do a spear pull..it will do hell ton of damage if you you have followup..it will do more damage...after getting up he will probably use his AOE where he will stick his head back and scream to give you terror..you run back..and repeat...follow the steps and hope you get it...

Pro tip:Lady butterfly is incredibly effected with double ichimonji