This is actually a good matchup for once and it does interest me. Not sure though but I am leaning towards Kisame as he has more than enough chakra to outlast Danzo. Kisame has good reflexes allowing him to dodge Danzo's basic wind attacks and even if he does get hit, he can heal with samehada or just absorb those chakra based attacks. Also Karin noted that izanagi used up a huge amount of chakra so this is a pretty bad situation for Danzo as samehada will overtime suck up his chakra meaning fhe won't be able to use izanagi for ten whole minutes most likely.
Danzo's summon Baku makes things interesting though, he can use it to swallow up Kisame and his water dome although I believe Kisame can beat Baku using his thousand shark jutsus coupled with an even bigger water dome. I think Kisame takes this with high difficulty as there is a threat that Danzo might be able to seal him.
