Why was Kisame surprised when he saw Obito (Tobi/fake Madara) without the mask the second time they've met in person? 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?
I dont believe this is a plothole, because the first time Kisame met the "Madara", it was actually Obito disguised as Madara Uchiha, Although we never got to see the actual person that Kisame was talking to, based of the way the persons hair from the Shadow was, it looked exactly like Madara Uchihas hair, and we all know that Obito's hair looks very different and isn't spiky long. (I would guess that Obito probably used substitution Jutsu in order to resemble the real Madara.)

However, the second time, he saw Obitos real face and that probably caught him by surprise since he was not expecting those scars.