How did Itachi obtain the MS?

[HamzaVeli]

Shisui's Death - was the trigger for his mangekyou sharingan - - there is or was no other way - - in his flashbacks with shisui he doesnt seem to have a mangekyou - and yet shisui does

[rai shado]

Itachi gained it by seeing Shishui die. Like the wiki says, you have to feel the emotion of having someone close to you die. Now this is a little ambiguous because sasuke got the ms by itachi sealing oro, at least thats what I remember. Now Kakashi had his best friend die a long time ago, Obito, if he found out how to obtain the ms then he might have just tried remembering that day, because Guy is still alive. We don't know how kakashi got it exactly and we will never know unless kishi tells us.