You might be wondering what the **** is this build and i'm here to explain it.
You might have encountered a yuumi player or an one trick and you found yuumi annoying this build is here to make her even better, everyone who uses these builds will become 100 times smarter, he will become so good that he can dominate in solo queue and maybe find a girlfriend who likes cats.

Pros

you don't need a teammate to play with in the botlane, you can go in every single lane you want, even Jungle!

you don't have any counters because you are the absolute BEAST you can counter everything. (Going to change this sometime in the future because apparently there is a lore)

For these builds to work you will need at least 3 items and you will be fed in seconds

Cons

Before your lvl 3-6 powerspike you can't win easily so you will need your jungler to help your you can just pray that your enemy sucks more than you do

Synergies
These builds are not perfect i'm still experimenting
Jax and Aatrox
Jax and Aatrox are yuumi's little helpers, you can hop on either of them and then when they are about to kill someone you W out and steal the kill like a chad
(WORSK MOSTLY ON AATROX WHEN HE DOESNT HAVE ULT OR ABILITIES)

Threats
Fiddlesticks is the holy weapon sent from god to destroy the evil yuumi, god gave fiddlesticks the power to silence and fear the cat so she cant do anything against him