It's not Shisui. The biggest argument everyone holds is "his body was never found"
BUT. Look at this:
(too lazy to post the photo, im on my phone)
Ao states here: his eye and right shoulder/arm is the same color as Shisui uchiha.
Meaning: after he killed himself, Danzo and his men retrieved his body and used/cut his right arm/shoulder as his vessel for sharingans. Danzo has possession of the body. If not, plot holes
BUT. Look at this:
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(too lazy to post the photo, im on my phone)
Ao states here: his eye and right shoulder/arm is the same color as Shisui uchiha.
Meaning: after he killed himself, Danzo and his men retrieved his body and used/cut his right arm/shoulder as his vessel for sharingans. Danzo has possession of the body. If not, plot holes