So, Kisame first met Obito (Tobi) when he introduced himself as the guy who controlls the Mizukage. Then, he tells Kisame about his Eye of the Moon Plan (Tsuki no Me) and recruits him to Akatsuki. So that's like 4 people who knew the true identity of Tobi as 'Madara' (later Obito, but they didn't know that): Konan, Nagato, Itachi, Kisame.
But if Kisame also knew him as the leader of Akatsuki, then why was he surprised when Tobi showed his face to him the second time, after Itachi died? I thought he already knew that Tobi mas Madara since he was the one who recruited him. It made sense for him to continue with Akatsuki after Nagato died, since Kisame didn't really care about who the leader was, as long as Kisame got the job done, but the only thing that bothers me is: why was he surprised when Tobi showed his face to Kisame the second time? He should've already known it was Madara/Obito. Is this a plot hole?