how danzo have a sharingan??

Well danzo can have a sharingan by having absorbed uchiha shisui's colored chakra into his right side of his body. Then he must have taken shisui's sharingan and transplanted it on his own eye. If you read the manga it shows that danzo can turn his sharingan on and off. This means he has to have the uchiha clan blood inside him. And no tobi and danzo are two very different people and I'm sure they don't share sharingans since danzo got it from shisui.

I am glad that I am up-to-date with the series, otherwise the discussion title would have spoiled it for me. Who is Shisui, you ask?

Warning: The following content contains spoilers.

Shisui was referenced earlier in the series. I am not sure where, if at all, it was mentioned in the manga, but in the anime it was when Sasuke's past was revealed, explaining why he hated/was seeking to kill his older brother, Itachi. In one of the flashbacks, it shows a group of men showing up at Itachi's door accusing him of murdering Shisui, who was, I believe, his best friend (my memory is a bit vague as it has been a long time since I've seen this). Itachi claims that he did not.

Its still not known whether he did or didn't (unless I am not remembering recent events correctly), but I am thinking that Itachi did not kill Shisui given the recent reveal of his true nature. Either way, Danzo has ended up with it.