A slight smirk came across Obito's face, but Madara wasn't able to see it.
"The Uchiha curse. Every man of our kin is bound to get affected by it sooner or later. If you still have unclear thoughts regarding this, then would you care to explain me why you are one of the most wanted ninja in this world? They want you dead, of course... In order to halt other advanced threats you make. Madara, I will continue on your legacy... if you lend me the power of Sharingan, that is."
Of course Obito was lying about the last part, however, even if he knew this guy can't easily get fooled, Obito had to try...