Rezarick

Rezarick is a Cleric-Accountant and a member of Black Sword Knights who serves as Isaac's adjutant (although he isn't actually the sub-guildmaster, and is instead its quartermaster).

In real life, his name is Kenta Yamazaki (山崎健太 Yamazaki Kenta), and he works as a funeral director.

Personality
Although appearing to be strict, Rezarick is actually a caring person. His personality, partnered with being a Cleric, makes him a reassuring presence during raids. Although he is a man of few words, he is earnest in his work and is attentive of other people's needs.

As the guild's quartermaster, he ended up shouldering the entire guild's administrative work on his own, and is suggested to be the one keeping the guild together behind-the-scenes, much like what Nazuna is to the West Wind Brigade.

Prior to the Catastrophe
Rezarick worked as a funeral director. His real name is Kenta Yamazaki, and he is in his thirties (around Isaac's age).

Round Table Conference arc
Rezarick appears behind Isaac, both of them eating Crescent Moon's hamburgers.

When Isaac and members of the Black Sword Knights are going for a nighttime training session, Rezarick inquires about Maryelle's and Shiroe's invitation to attend the Round Table Conference, and informs Isaac about Maryelle's failed attempt to unite some of the small guilds. He accompanies Isaac to the conference and watches as the discussion unfolds. When the Black Sword Knights visit the Log Horizon guild building, Rezarick accompanies them despite not being a Summoner.

Ragranda Forest arc
Rezarick is one of the members of Black Sword Knights sent to accompany the beginners in their summer camp. He listens to Isuzu playing her lute with the other trainers. Alongside Log Horizon members Naotsugu and Nyanta, he accompanies the dungeon group to Ragranda Forest and sets up a temporary camp for the beginners at the dungeon's entrance. He becomes a reassuring presence for the beginners who are to challenge the dungeon everyday in order to gain experience.

He is the only member of his guild that went to Ragranda Forest, as the others went to Sand Leaf. When the group is attacked by waves of goblins, both he and Naotsugu ponder this unusual circumstance, with Rezarick pointing out that the encounter rate shouldn't be this high. Later, after setting up camp, Nyanta talks about how he spotted around an army of over a thousand Goblins, much to the player's shock. After Nyanta mentions that he couldn't contact Maryelle or Shoryu, Rezarick attempts contacting the Black Sword Knights members at the beach to no avail. Once Nyanta finishes his assessment of the opposing group, Minori and her group speak up, having heard the conversation. Serara and Isuzu contact the members of the Crescent Moon Alliance that were at the beach to learn of their situation. Shortly after, the entire Ragranda group gather in the tent to discuss their strategy. They learn from the description from one of the Crescent Moon Alliance members that there were "blue goblins" overrunning the beach. Although Rezarick asks if it was a coincidence, all three veterans are aware that it was most likely not one. He is present when the two groups meet back up, and attempts to dissuade Minori's party from going to save Choushi. When they do so anyways, he is part of the four-man group that goes to assist them.

Libra Festival arc
Rezarick is present by Isaac's side, and he and Misa are seen bowing to each other in respect.

Route43 arc
As Isaac's adjutant, he accompanies the guild master to one of several meetings with Shiroe about the plan to have the Black Sword Knights help train the Eastal knights in order to strengthen their relationship. After Isaac takes credit for doing the work that Rezarick did, he takes a sort-of revenge by calling Isaac "Isaac-kun," which the guild master detests.

Homesteading the Noosphere arc
At Maihama, Rezarick joins Isaac, who had been sent to sit off to the side because he was too rough with the Lander knights, after Rayneshia's younger brother Icelus began bothering him. Rezarick then teaches Icelus to call Isaac "Isaac-kun," and laughs at Isaac's annoyance before returning to the training knights with Icelus.

While Isaac initially brushing of Icelus as "just a rich kid," Rezarick stayed by Icelus' side when Isaac hung back, accompanying the boy when he was looking at swords. When Isaac chides Icelus for looking at a sword that was decorative instead of practical, then tells Rezarick he should have stopped the boy, Rezarick replies that Isaac was better at judging swords. Rezarick is present for Icelus' birthday banquet; when the Westelande assassins reveal themselves, Isaac tells him to hold them off as he takes Icelus to safety. Once Isaac dealt with the assassins that pursued him, Rezarick and Charasin arrive, with Rezarick offering to heal his debuffs.

Honey Moon Logs
During the Round Table Conference, Rezarick is seen trying to calm Isaac down after Shiroe reveals that he had bought the Guild Meeting Hall.

Log Horizon SNG
Rezarick is a recruitable character in Log Horizon: New Adventure Land.

Trivia

 * Rezarick shares a voice actor with Lord Darte, HighlandSky, and Ragoumaru.