So to begin with, from another thread by UchihaMadara01 qoutes another user,
In a thread Called "Tobi cannot use space time jutsu when kakashi uses kamui"
The creator of the thread said this.
It says that there eyes are a pair, which I think is correct. Also that means Tobi had to do something to get the MS, kill someone dear to him or something happens to someone dear to him.
First I think Zetsu saved Obito while Obito got crushed and Zetsu always roams to get Info.
Then because we don't know about Rins ware abouts I think she died during the war and Obito might have seen or heard of this and because she is very dear to him Obito unlocked the MS
Now Kakashi not knowing about himself having the MS probably never tried to unlock it because if he lost Obito and Rin to very dear people to him he would have unlocked on his own and gotten MS because he has the eye but I think only Uchihas can unlock it further.
Now since Rin had died I think Obito learned about the ways of how people are and subdued by the Akatsuki takes all his hatred and becomes the evil Tobi he is now.
So to prove you can get MS from losing someone dear to you is Itachi and Shisui. Itachi never killed Shisui, so Itachi got his eye from losing him.
Now tell me what you think yeah
Also I thing I used the wrong vocab and grammer
Please respond and if you think which parts you think are or maybe correct please say