Mangetsu Hōzuki

is the elder brother of Suigetsu Hozuki, who is currently a member of Team Snake. He was probably well-acquainted with the current Mizukage earning him and his family special privileges among most shinobi of Kirigakure. He was most likely also a member of the Seven Swordsmen of the Mist, usually partnered with Kisame Hoshigaki, which is probably why Kisame recognizes Suigetsu and acknowledges the mention of Mangetsu's name during Sasuke Uchiha's hunt for Itachi Uchiha.