Sharingan exchange

[verdesnake]

Why do they have to kill each other? They could just exchange eyeballs. Um, duh.

[iron_maiden]

itachi said that the uchihas killed their friends in order to awaken the MS and then took their siblings MS in order to attain the EMS.

[Shock]

Well I think they have to take the others eyeballs and eat them or something in order to get the Emergency Medical System because they somehow combine into making a better eyeball that won't burn out so fast or something. idk details aren't clear as of yet.

[UchihaRyken]

They can't explain eyes because they have to permanently infuse the other's eyes into their Sharingan monster thing.

Spoiler!

Also, I believe this was discussed in another thread. Maybe you should look around for more in-depth answers.

[Shawshank]

I wonder how many people still think it's a transplant. It's a fusion, not a transplant.

They can't just exchange eyes because they need to fuse their eyes from the eyes of their siblings so you have to take them.