Yuuki Kagurazaka

"“Isn't that obvious? Let's make sure we rule this world. And then we will all live happily ever after!”"

- Yuuki

Yuuki Kagurazaka (神楽坂優樹) is a Japanese Otherworlder summoned into this world and the one who made the Free Guild into what is today. He can be considered initially an antagonist, and later on, an ally of Rimuru Tempest.

Appearance
He's considered fairly handsome, with black hair and black eyes. He looks as young as a middle schooler despite his real age being in the twenties.

Personality
Yuuki's fundamental dream is world domination. Extremely greedy and ruthless, he has demonstrated the ability to dabble in the selling of otherworlder children in order to achieve his goals. However, that is not to say he is without morals as he has demonstrated distaste for slavery. He is extremely cunning having manipulated other masterminds such as Mariabell and Granbell Rosso to their demises. He also instigated Hinata Sakaguchi in order to make her try kill Rimuru. He has a history of betraying others in order to benefit himself. Being a natural genius, he is capable of maintaining a facade extremely well.

He is quite loyal to his friends and allies in the Moderate Harlequin Alliance.

After the death of his parents he vowed to change the unfair world that caused him and others suffering unnecessarily. He has a naive and childish goal of 'World Peace', wanting to create a world where him and his friends can laugh and have as much fun as they want.

Background
A natural born genius, Yuuki was satisfied with his life on earth. He had loving parents and plenty of friends. But after an overworked truck driver fell asleep at the wheel and crashed into his parents car killing them both, he fell into despair. When the courts ruled the driver innocent, Yuuki discovered the unreasonableness and flaws of society. He initially wanted to take revenge and tear it all down but couldn't bring himself to inconvenience so many innocent people in the process. Instead, he realized that he would have to change society one step at a time by becoming a politician and gaining like minded friends and allies who would help him achieve a more fair society. But before he could even finalize his plans he was summoned to the Central World.

Kagali, a former demon lord on the verge of death due to their defeat at the hands of Leon Cromwell, had summoned Yuuki whose material body and spiritual body was compatible with their astral body and attempted to, with the last of their strength, lay a curse on Yuuki that would kill his spirit instantly and allow them to reincarnate into his body. However, Yuuki being a genius who already understood how the world worked during the trip between worlds, had awakened his Unique Skill Creator and used it to make his special constitution, Anti-Skill, letting him resist the curse. Yuuki, taking pity on Kagali, allowed them to inhabit his body and promised to find a body for them to reincarnate into, saving her life and giving her hope.

After letting Kagali inhabit his body, at some point he wound up under the tutelage and guidance of Shizu alongside fellow student Hinata Sakaguchi, who were both Japanese countryman. There he learned about the world's language and society. Alongside his teacher, Yuuki used his knowledge of a more modern world to rework the society of adventurers into the internationally accepted Free Guild, which he was then appointed Grandmaster of. Under his leadership, monster related deaths decreased dramatically and a new system of ranking monsters based on their amount of Magicules and other factors was established. These changes allowed for trade to blossom and the population to boom in areas that were previously poor and decrepit, improving the lives of many.

At some point, Yuuki encountered Mariabell Rosso who was secretly manipulating society and the economy from behind the scenes via the Council of the West, which she had complete control over. Mariabell stood as an absolute roadblock in Yuuki's goal of a fair and just society and blocked his plans off at every turn, much to Yuuki and Kagali's annoyance. At sometime Yuuki met Damrada and crushed the dark organization in the east known as "Echidna," reforming it into the underground organization Cerberus a place where he and his friends could be at last free from Mariabells eyes and ears. He appointed Vega, Misha, and Damrada as its leaders. Eventually, an opportunity to strike back at Mariabell came when she attempted to dominate him with her Unique Skill Greed. Yuuki managed to resist her domination due to his "desire" being stronger than hers and used his position to secretly influence Mariabell's mind and actions in return.

Trivia

 * Yuuki is one of the characters who had been changed the most between the Web Novel and the Light Novel. His entire character has been reworked and his motivations are completely different, to the point that his actual "role in the story" is a completely different one in the Light Novel compared to the Web Novel. In the Web Novel, he was the main antagonist.
 * If Yuuki converts all his energy into magicules, he could rival the likes of Luminous and Leon.
 * Yuuki's English Voice Actor, Clifford Chapin, also voices Gobzo.