Yuuki Kagurazaka/Chronology

Human-Monster Interaction Arc
Heeding the recommendation of Fuze, he met Rimuru Tempest, a slime who had purportedly murdered his teacher Shizu and taken her appearance. Rimuru, to his surprise, also turned out to be a fellow countryman and after explaining the circumstances of Shizu's death, which Yuuki begrudgingly accepted. The two got along well and Rimuru's gifts of recreated manga and stories of what happened since his summoning in Japan greatly pleased him. Yuuki accepted the last wish of his teacher and allowed Rimuru to take her place and teach the students of Class S, Summoned children who Yuuki had taken into his care that were too young to handle their own power and doomed to eventually perish.

Demon Lord Awakening Arc
While Rimuru was acting as a teacher, Yuuki sent Kazalim's subordinate, Laplace, in order to gain information on the Western Holy Church's headquarters in Ruberios, believing it to be a corrupt organization that stood in the way of his ideals. At the same time he had Kazalim's demon lord successor, Clayman, attempt to control demon lord Milim Nava and gather souls in order for Clayman to awaken as a True Demon Lord. However, learning that the initial plan of awakening Clayman via the destruction of Eurazania had failed, he set his sights on accelerating the start of a war between Tempest and Falmuth, which had gained too much power and influence via the mass summoning of otherworlders, ideally so he can gain souls for Clayman's awakening at the same time. However things didn't go according to plan. Rimuru who he sent Hinata Sakaguchi to kill on his return trip to Tempest, had somehow survived and the entire Falmuth army died at his hands. Even their bodies and souls were nowhere to be found, leaving Yuuki slightly anxious that Rimuru had summoned some kind of monster offering them as sacrifice. Falmuth being weakened by their defeat was an acceptable result, but Rimuru who survived and was much stronger than expected would undoubtedly become suspicious of Yuuki and make it harder for him to move, making the entire ordeal a massive pitfall that Yuuki regrets falling into deeply. Meanwhile Laplace, who had returned from his infiltration, reported the the pope was in fact a vampire, and with the help of Kazalim who had now inhabited a homunculus and taken on the name Kagali, they were able to confirm his identity, Demon Lord Valentin.

The Octagram Soars Brightly Arc
Nevertheless, even without Hinata, Yuuki still had a means of dealing with Rimuru before things got out of hand. He had Clayman use Frey and Millim to start a Demon Lord's Banquet in order to have the rest of the demon lords unite to take on Rimuru, hopefully destroying him before he became a problem. But things seem never go as planned when it comes to a certain slime, Rimuru had somehow managed to attend the banquet himself and turn the demon lords against Clayman, gaining their support to take his place before killing Clayman himself. With Clayman dead, it left both him and the rest of the Moderate Harlequin Alliance to mourn his loss in defeat.

Monster Capital Opening Festival Arc
After things settle down, Yuuki accepts Rimuru's invitation to the Tempest Opening Festival reuniting with both Hinata and Rimuru, as well as having a good time enjoying the nostalgic foods and music. Mariabell as well as several of her collaborators also attended the festival and he took great joy in seeing them try and fail to trifle with Rimuru. While there he also got a good idea of Tempest's military might which was so outrageous that he instantly cut any thoughts of making them enemies from his mind and leaving only ideas of further cooperating in the future.

Hero Awakening Arc
Cutting his losses with Rimuru and the Church mostly short, Yuuki decides to focus all his efforts into overthrowing the Rosso clan and their influence in the Western Council. Mariabell, who saw Rimuru as an enemy to her goals of economic domination, planned to attack him during his exploration of the ruins of Amalita, which was Clayman's former domain that was also once the capital of Kazalim's country of dark elves. However, due to Yuuki's deception and mental manipulation, her plans had become sloppy and full of openings. Yuuki took the opportunity to personally kill her off, Stopping her tyrannical rule from ever happening as well as gaining her unique skill Greed and blaming all of his shady actions on Mariabell in the process.

Reflecting on the conflict with Mariabell, he was able to figure out that the "God" of Luminism was actually Luminous Valentine, a demon lord. Negotiating with Mariabell's great-grandfather and head of the Rosso clan, Granbell Rosso, they devised a plan to take down Luminism by unleashing the incarnation of evil itself, Chronoa, in Ruberios while demon lord Luminous was distracted with demon lord Rimuru's performance. The plan ended up backfiring horribly for Yuuki, who was tricked by Granbell, and he had to abandon all his operations in the west and flee east due to being completely exposed to Rimuru.

Eve of War Arc
While fleeing Ruberios and planning to regroup with Kagali so they could move all their operations to the Eastern Empire, Yuuki was confronted head on by the "Lord of Darkness" and original demon lord, Guy Crimson, who proceeded to beat Yuuki into the ground. Even unleashing all his power of Anti-Skill and Creator evolving him from a regular human to a fully spiritual saint in the process, as well as using his intrinsic psychic abilities, it wasn't enough to leave even so much as a scratch on Guy's body. Yuuki, realizing Guy's intentions, manages to negotiate for his and his friends survival in exchange for them doing their best to help destroy the Eastern Empire from the inside. After the fact, frustrated by his own lack of power and inability to protect his friends, Yuuki reached inside himself and managed to awaken his Unique skill Greed into Ultimate Skill Mammon, Lord of Greed.

After fleeing the west, Yuuki took asylum in the Eastern Empire. Joining its Imperial Guardians, he managed to beat many of his seniors, and in just a matter of months, rose to the rank of division commander, one of the highest positions within the military.