Tsuare Rescue Mission was an assault carried out by Nazarick as part of Operation Gehenna to rescue Tsuare from Eight Fingers. They also received cooperation from forces from the Re-Estize Kingdom, who were having their own conflict with the criminal organisation.
A small war had taken place within the kingdom, between the Re-Estize Royal Family led by Princess Renner and the criminal organization, Eight Fingers. The princess's aim was to save her kingdom by expunging Eight Fingers who had been responsible for most of the country's major crimes. To accomplish this, Renner had brought in like-minded individuals to her cause and hired adventurers, such as the Adamantite-ranked Adventurers, Blue Roses. The two forces were seemingly locked in a stalemate until the forces of Nazarick were involved in it.
Sebas Tian has been living in the Re-Estize Kingdom while working undercover for his king. One day, Sebas discovered a brutalized slave girl named Tuareninya and took her in to take care of her. Unfortunately, this drew the attention of Eight Fingers who were the owners of that girl. They tried to threaten Sebas to give her up but this resulted in retaliation from Sebas's part who had killed many of their members and got one of the Six Arms arrested.
Sebas returned home and discovered that Ainz Ooal Gown was present. The Sorcerer King had been contacted by Solution Epsilon who was also acting as a spy and informed him about Tuareninya. Despite Sebas disobeying his commands, Ainz forgave him. After Sebas proved his loyalty to him, he chose to have the girl under his protection after he realized that she was the older sister of Ninya.
While Sebas and Solution were out, Eight Fingers infiltrated their home and kidnapped Tuareninya, intending on using her to kill Sebas. It wasn't long the two discovered this and reported back to Ainz. This incurred Ainz's wrath and he ordered all the Floor Guardians to travel to the Re-Estize Kingdom and aid Sebas in rescuing the girl along with the additional goal of eliminating Eight Fingers once and for all.
While the Floor Guardians carried out their specific tasks, Sebas and Solution who stayed within the shadows head toward the location where Tuareninya was kept. When arrived at his destination, Sebas encountered Brain and Climb. The two were part of a team with an Adventurer named Lockmeier. They were sent by Princess Renner who had assembled her forces to take down the criminal organization. Seeing that their goals were aligned, Sebas joined forces with them.
The group formed a plan with Sebas distract the criminals while the others snuck inside the building to find and rescue Tuare. After entering through the main gate, he encountered four members of Six Arms, their minions and corrupt nobles who were watching the spectacle. They declared their intentions towards who they considered as an old man, punishing him for defying them. Despite being outnumbered, Sebas did not pay mind and challenged Six Arms for a fight and that should they fight together, they would at least last ten seconds. While in secret, Sebas ordered Solution to converge on the nobles.
Angered at being looked down upon, Six Arms accepted the challenge. All of Six Arms revealed their names with the last one being Davernoch, the Undead King. Unfortunately, Sebas was completely enraged that someone he deemed unworthy had used a title belonging to Ainz and made a mockery of it. He didn't hesitate to blow Davernoch's head to pieces, killing the Elder Lich.
The next member to fight was Edstrom but it was over before even she knew it having being decapitated. She still had some consciousness left before her head hit the ground. The last two members, now in a panic, attacked Sebas together. He held their blades with ease before finishing off Peshurian. Malmvist had gone completely insane after seeing three members of Six Arms decimated by Sebas who casually ignored him for the moment and took off his gloves. Malmvist jumped to get the gloves, believing they are powerful items before laughing in the madness that he might be safe. Sebas allowed him to be this way out of pity and proceeded to kill him. After Solution confirmed that there were no more additional forces, Sebas, and her start to kill all the whimpering criminals and nobles before rescuing Tuareninya.
Meanwhile, Brain, Climb and Lockmeier head to a cell and found a woman who might be Tuareninya. This turned out to be a trap by Zero and the woman was actually Succulent using magic to disguise himself. A battle took place with Brain dueling against Zero while Climb and Lockmeier battled Succulent. Despite Succulent hiding within his illusion clones, Lockmeier counteracted them using items to detect him. Climb took this opportunity to defeat him, striking at the groin.
Brain and Zero were at a stalemate causing both of them to end this using their most powerful techniques. Before the two fighters could do anything, Sebas arrived with Tuareninya. Zero was puzzled, especially after Sebas claimed he defeated all of his team members. Refusing to believe Sebas to be stronger, Zero fought him and used his most powerful attack. It made contact with its intended target but Sebas endured it, without a scratch on him. The butler made short work of the shocked Zero who was killed with a swift kick into his skull.
With Six Arms dead, Eight Fingers lost their means to maintain order within the organization. However, the worse was far from over. The forces of Nazarick had already taken over most of their operations and eventually, Hilda, cracked under the pressure of the torture she endured, betrayed her compatriots to them.