I always assumed....

[HokageKid]

I always assumed each Uchiha whom had unlocked the mangekyou sharingan, gained 3 abilities.
One in the left, one in the right and then one from the combined efforts.
Because Itachi and Sasuke both had Amaterasu, Tsukuyomi, and Susano'o
Obito would have had his absorption/intangibility technique, and kakashi's Kamui, and presumably another third technique had he kept both eyes
and Madara is presumably a direct ancestor to Sasuke and Itachi, has shown to use Susano'o so may have Amaterasu and Tsukuyomi also, but that's not known yet because he hasn't used any other EMS techniques.
So how come both of Shisui's eyes simply had Kotoamatsukami?
I'm probably completely wrong about something ahaha

 

[Made in Heaven]

Because sushi isn't important enough to be given more than 1

 

[Masterpiece7]

I think kotoamatsukai was simply a normal genjutsu,that's just my opinion tho.

 

[Corgi]

It's just two abilities. One in each eye. The third ability is using Susano'o.

Itachi - Amaterasu and Tsukiyomi

Sasuke - Amaterasu and supposedly Enton and controlling it. He should have Tsukiyomi but either he's just bad with Genjutsu or doesn't use it, as Obito himself said Itachi transferred all his techniques to Sasuke upon death.

Obito - Physical contact sends to other dimension (right eye), ocular sight sends to other dimension (left eye)

Kotoamatsukami in itself is pretty OP. He didn't get enough screen time to fully understand his abilities.

 

[HokageKid]

I think kotoamatsukai was simply a normal genjutsu,that's just my opinion tho.

It's seen being used via Mangekyo Sharingan, by the world's most powerful crow

 

[WreckRoll]

not everyone has 3 abilities, as obito pointed out

 

[Inert Brian]

Obito stated at the Kage summit that "An Uchiha with MS and Susano'o is a rare sight" This was during the time when he explained the moon eye plan to the kage.

Madara has shown to be able to use Tsukuyomi, he trapped Ay in it when they were fighting all the wood clones w/ susano'o