Gengetsu Hōzuki

He was the of Kirigakure.

Background
During his lifetime he seemingly had a significant and mutual rivalry with the Second Tsuchikage, Mū. Eventually, this contestant relationship would lead both men to their deaths, as they each successfully manage to kill each other during a confrontation.

Appearance
The Second Mizukage is an individual with a fairly tall and slender stature in comparison to others. His elongated face is accentuated by his relatively long light-colored hair, worn in a combed back style, and the presence of a small dark-colored goatee and thin moustache. Due to the effects of the Summoning: Impure World Resurrection technique, he has black sclera and white irides.

His typical attire consists of an extremely long sleeved and high collared light-coloured jacket, which descends to below his knees and displays the prominent pin-striped patterning that is common amongst the shinobi of Kirigakure. This article is worn over a dark-colored and high necked suit, with an equally dark sash wrapped around its exterior at his waist.

Abilities
Although he has yet to be observed in combat, the simple fact that he was able to kill Mū, albeit at the cost of his own life, stands as an appropriate testament to his proficient skills. This is because even some of the most notable shinobi of the Allied Shinobi Forces greatly feared that no one but Ōnoki, a former pupil and possessor of the same kekkei tōta as Mū, would be able to stop the former Tsuchikage, suggesting that the Second Mizukage's combat capabilities are truly fearsome.

Shinobi World War Arc
Due to the undesirable circumstances born from the detection of Mū's concealed approach towards the Fourth Division, Kabuto Yakushi resolves to not fool around further and so, with this intention in mind, he summons three other Kage to Mū's present destination to provide adequate support. Amongst this number is the Second Mizukage, who immediately notes both the deliverance of his most bitter adversary, Mū, and the presence of others that he doesn't recognize, i.e. the Fourth Kazekage. Questioning the subsequent explanation of the situation, he strongly asserts that at the time of his death, he also killed Mū, which is quickly yet begrudgingly agreed to by the individual in question. As the conversation continues with the divulgence of the bounds of the technique that ressurected them, the Second Mizukage concludes that what is stated is correct, as he was currently contemplating killing Mū again but wasn't able to as his body isn't responding to his thoughts.