“That Time I Got Reincarnated as a Slime” Story Summary — The Great War with the Eastern Empire (Full Spoilers!) A detailed summary reconstructed from video content, covering
A detailed summary reconstructed from video content, covering everything from the post-founding festival era, the Western Council meeting, all the way to the Great War with the Eastern Empire (equivalent to Light Novel Volume 10 onwards). This contains full spoilers! For anyone who loves deep details, highly recommended to read until the end!
The story begins with Yuuki talking to Kagali and Laplace, reviewing the development plan for the city of Tempest. Yuuki talks about the strange new technologies and innovations he witnessed, and because he is currently suspected of leaking information regarding Shizue-sensei, all their plans have to be put on hold for now.
The group evaluates Rimuru’s strength, noting that while he looks friendly and not particularly intimidating on the outside, his gaze seems to pierce through everything. Yuuki sees no benefit in making an enemy out of Rimuru since there is no profit in it. Meanwhile, Kagali volunteers to test Rimuru’s power herself, taking advantage of Rimuru’s upcoming expedition to explore the ancient ruins beneath Clayman’s castle—which was originally an elf kingdom with defense mechanisms built by the former Demon Lord Kazaream. Yuuki permits Kagali to proceed but instructs her to only gauge his power level and not overdo it.
Back in Tempest, three days after the conclusion of the Founding Festival, the economy is booming massively. However, one issue arises with the Dungeon business. The number of adventurers has multiplied, but not a single group has managed to clear the 1st Floor. This is because everyone is solely focused on grinding for gold inside the dungeon, ignoring strategy guides and neglecting to map out the layout.
Rimuru calls a meeting with the dungeon creators to overhaul the system, making it feel more like a video game. They increase the item drop rates in treasure chests, add save points, create warp doors connecting to lodgings on every floor, and balance the difficulty to be challenging but achievable. A grand prize of 100 gold coins is announced for the first five groups to conquer the 50th floor, along with rewards for every 10 floors cleared, which will reset the following month. This is intended to motivate nobles into sponsoring adventurers. The adjustments work perfectly; adventurers start taking the conquest seriously, and Masayuki helps fire up their morale, leading them to breach the 30th floor.
Rimuru rewards Diablo by granting him one wish. Diablo asks for permission to go out and recruit old acquaintances from his past to come work for them. Rimuru grants permission and prepares 1,000 homunculus vessels as requested. Initially, Rimuru misunderstands, fearing Diablo is building an army to overthrow some nation, but ultimately lets it slide and allows Diablo to depart. Afterwards, Rimuru asks Ramiris to construct a massive hall on the 100th floor of the dungeon and locks himself away for three days to refine the 1,000 vessels for the demons to possess.
While Rimuru is in seclusion, Myourmiles reports an urgent issue: a mysterious group named Team Ryokuran (Green Envy) has used brilliant tactics to rapidly pierce through to the 40th floor. This worries Rimuru, as he intended for Masayuki’s team to conquer the 50th floor first. Upon inspection, they find that Team Ryokuran is A-ranked, and their green-cloaked leader, utilizing the insignia of an organization named “Veil”, possesses power that far exceeds Rank A.
At the same time, the Holy Knights led by Hinata Sakaguchi begin their descent from the 51st floor, successfully reaching the 60th floor. Goaded by Fritz into saving face, Hinata pushes forward all the way to the 95th floor in a single day, shocking Rimuru. Ramiris explains that Zegion has entered a cocoon-like slumber, and Apito, still lacking experience, was defeated. Furthermore, the Dragon Faithful guardians and deadly trap rooms proved completely useless against Hinata, allowing her to storm into the 100th floor.
On the 100th floor, she encounters Veldora, the ultimate guardian. Hinata’s attacks do absolutely nothing to him. She employs an attack similar to the one used by the person who sealed him in the past, but ultimately faces defeat. Raphael cannot retrieve the battle records because Ramiris tore them up. Rimuru completely redesigns floors 61–90 and helps Adalmann master Holy Magic to become stronger. In the next meeting, Milim, who was furious that her dragon lost, calms down. Gobta and Ranga, who went for special training with Milim, also return.
Rimuru brings orbs that can shape-shift based on one’s imagination and distributes them to Ramiris, Veldora, Milim, and himself. By having each person visualize their favorite monster, the orbs transform into monster avatars. Everyone can transfer their consciousness into these bodies with the purpose of jumping into the dungeon on the monster side to drive out intruders. Rimuru has Kurobe craft powerful armor and weapons, allowing everyone to develop character classes. They immediately initiate combat against Team Ryokuran.
Mariabell is an Otherworlder from Europe, where she once ruled as a leader, pulling the strings of economy and corruption from the shadows. She lived a life of ultimate indulgence until her passing, after which she was reincarnated as the princess of the Rozzo Kingdom (Silotzo). Born with an insatiable desire to possess everything, she acquired the Unique Skill “Greed” (one of the Seven Deadly Sins series).
At the age of three, she aligned her ideals with Granbell, one of the Five Elders who holds massive authority within the Western Council, leader of the Rosso Family and the former Elder Sunday. Mariabell’s desire is to completely dominate the economy of the Western Continent. She has been the puppet master behind the Western Council until Rimuru appeared, causing the network she controlled for so long to destabilize. Astonished by the exponential growth of Rimuru’s city, she believes Rimuru will eventually control the global economy and aggressively plots to eliminate him as quickly as possible, falsely operating under the assumption that Rimuru is weak.
Rimuru receives an invitation and travels to the Kingdom of Ingrassia accompanied by Benimaru, Shuna, and Souei. Prince Elrick of Ingrassia asks Hinata to join a plot to test Rimuru during the council meeting. However, Hinata views it as foolishness, refuses, and warns him not to pull the tiger’s tail—but Elrick refuses to listen.
The agreement presented to Tempest is incredibly selfish. The terms demand that Tempest shoulder all construction costs for the Magitrain themselves, grant the Council administrative rights over the Labyrinth, and pay an annual tax. Rimuru is infuriated by this sheer ignorance, flips the table, and sits arrogantly cross-legged, terrifying the council members. Raphael informs him that most people in the room are currently manipulated by Greed, prompting Rimuru to order Raphael to release them.
Suddenly, Prince Elrick storms in, declaring his intention to subjugate Rimuru. Shuna and Hinata step in to deflect the attacks from Elrick’s subordinates. Rimuru’s Magic Sense then detects a sniper shot from 2 km away. Glenda, an assassin of the Rosso Family, fires a spatial-transcending bullet aiming for Prince Elrick’s head (to frame Rimuru for murdering the prince). However, Rimuru uses Beelzebuth to swallow the bullet just in time, ruining the framing plot and allowing Rimuru to finally join the Western Council.
Glenda is an assassin for the Rosso Family, summoned with her past memories intact, possessing the Unique Skill “Sniper”. Souei engages her in combat. Glenda miscalculates, thinking Souei is just an ordinary target, resulting in her utter defeat. Rimuru interrogates Glenda, but she refuses to answer, so Rimuru lets Raphael take over. Raphael calculates and pieces together the entire plot out loud, bringing Glenda to tears over how much Rimuru knows. She confesses everything is true. Rimuru understands and releases her bonds. To his surprise, she asks to join Tempest instead. Rimuru accepts her into their ranks and leaves her in Souei’s hands for strict training.
Rimuru orchestrates a countermeasure, luring Mariabell into a trap within the ancient ruins. Mariabell appears alongside Yuuki and Gaiji, both of whom she has allegedly brainwashed. She attempts to use physical and magical attacks to no avail, so she deploys Greed to dominate Rimuru’s mind. However, her Unique Skill proves entirely ineffective. Desperate, Mariabell decides to detonate the elemental reactor on the lowest floor to drag Rimuru down to the grave with her.
But when Mariabell reaches the bottom floor, the reactor is nowhere to be found—she was tricked by Yuuki! Yuuki catches up and assassinates Mariabell on the spot, stealing the Unique Skill “Greed” for himself. Later, Raphael reveals the truth that Yuuki was acting entirely on his own accord, merely “pretending to be controlled.” Rimuru changes his stance, deciding to remain on guard and closely monitor Yuuki until the very end.
Laplace meets with Demon Lord Leon regarding a contract involving trading Otherworlders. Leon learns from Tear that there are five Otherworlder children staying with Rimuru, and the name “Chloe” catches his attention, making Leon suspect she is the very child he has been searching for all this time.
Tempest has nearly completed the construction of the Magitrain. Rimuru analyzes his own sword, which has been bathed in such dense magicules that its properties have transformed into “Hihiirokane”—a legendary metal that never corrodes and can evolve up to God-grade (Mythical). A new problem arises as they face a shortage of judicial officers and legal infrastructure. Rimuru decides to wait for Diablo’s return. Shortly after, Demon Lord Dino (The Sleeping Ruler) arrives asking for a place to stay in Tempest. Rimuru strikes a deal stating that if he wants to stay, he must work. Dino complies upon seeing that even Ramiris and Veldora have to work.
Diablo returns with three guests who look like cute young girls, but Raphael informs Rimuru that they are actually Archdemons over 1,000 years old (Primordial Demons). The three report that a total of 700 subordinates have come to pledge their loyalty. Rimuru names the three demonesses after sports cars—the white-haired one is “Testarossa”, the golden-blonde one is “Carrera”, and the purple-haired one is “Ultima”. He provides them with powerful physical bodies, refines their beauty, and fuses gold into their skeletons, triggering their evolution into Demon Peers.
This marks the birth of the strongest military force named the “Black Numbers”. The three demonesses wholeheartedly accept Rimuru and are appointed to crucial roles: Ultima becomes the Chief Prosecutor, Carrera becomes the Chief Justice, and Testarossa becomes the Chief Diplomat representing Tempest in the Council while managing the forces.
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Luminous invites Rimuru to perform a musical concert in Lubelius. On another front, Granbell conspires with Yuuki to launch an assault on Lubelius, planning for Yuuki to steal the Sanctuary Box kept by Luminous, which contains the body of the Hero who once sealed Veldora.
During the musical performance, Granbell invades with his forces. Granbell proves remarkably powerful, fitting for a true former Hero. He aims his blade at Chloe. Hinata rushes in to shield her, sustaining fatal injuries that cause her soul to begin dissolving. At that moment, a bizarre phenomenon occurs; as Hinata’s hand touches Chloe, both emit a brilliant light and vanish together!
The Secret of Time Travel: Hinata and Chloe are flung 2,000 years into the past. Chloe reveals that she possesses a time-leaping skill and has been trapped in this endless loop. In previous timelines, Rimuru never became a Demon Lord and died during the war with the Empire, resulting in the collapse of Tempest. Driven by her desire to save Rimuru, Chloe kept leaping through time. Adopting the name “Chronoa”, she traveled through history saving humanity and ultimately sealed Veldora (with Hinata controlling the body). Afterwards, Chronoa’s body had to be entrusted inside Luminous’s Sanctuary Box, awaiting the time Rimuru would come to save her in the future.
While Hinata and Chloe are missing, the battle rages on. Diablo fights Rain (the Primordial Blue), while Shion and Ranga eliminate Razul. Luminous engages in a fierce clash with Granbell. Granbell loathes a world that tore his precious loved ones (Maria and Mariabell) away from him, driving his desire to awaken the Hero’s body. Ultimately, Guy Crimson appears to put a stop to the demons’ duel. Guy and Diablo are old acquaintances, and the three-way balance among the Primoridals that Guy maintained for millennia is beginning to fracture because of Rimuru.
At the Western Council, Johann Rozzo stages a rebellion, ordering the barrier to be detonated and summoning a divine entity: Misery (the Primordial Green). However, the aura of death proves completely ineffective against Testarossa. Misery realizes that Testarossa has received a name, a physical body, and has likewise evolved into a Demon Peer, choosing to retreat as she cannot guarantee victory. This event earns Testarossa immense trust and restores command authority back to the council.
Guy is infuriated that Rimuru named three Primordials, prompting Diablo to explain Rimuru’s grand scheme. Rather than ruling through fear, Rimuru chooses to distribute wealth, build international relationships, and establish a new economic system that allows humanity to choose its own future. This system will weave itself into human society almost permanently, with Rimuru as the ultimate controller. In the end, Rimuru is officially appointed by Guy as the leader of the Western faction, turning their focus to preparing for the conflict with the East.
One year passes. Rimuru organizes his military into three main corps: the 1st Corps (Gobta), the 2nd Corps (Geld), and the 3rd Corps (Gabiru), supplemented by special units (Benimaru’s Kurenai unit, Souei’s Kurayami unit, and Shion’s Yomi unit), totaling over 100,000 troops, alongside their trump card: the 700-strong Black Numbers. Tempest has officially become the economic epicenter of the Western faction, successfully completing the Magitrain and stockpiling enough provisions to last a full year under siege.
Yuuki holds a meeting with Gadra, a thousand-year-old mage, and dispatches his three Otherworlder disciples to investigate the dungeon. The three manage to break through to the 59th floor, catching Rimuru’s eye. Rimuru organizes an evacuation drill, “moving the entire city” inside the dungeon, explicitly to catch the attention of and bait the Empire into sending spies. Gadra secures an audience with Rimuru, only to discover that his dear friend Adalmann is still dynamic and well. Gadra consequently decides to betray the Empire to serve Rimuru instead.
The mysterious female Grand Marshal standing beside the Emperor reveals herself to be Velgrynd, the Scorch Dragon. She has been playing a game of world domination alongside Emperor Rudra for millennia—Rudra playing the human side, while Guy Crimson plays the demon side. The core condition dictates that the primary players cannot step onto the battlefield themselves. The Imperial army mobilizes a massive force totaling over 1,130,000 troops!
The Imperial magi-tanks and airships breach Tempest territory. Rimuru declares a “Black Line,” warning that anyone who crosses it chooses war. The outcome is a total wipeout: Gobta and Ranga crush the tanks, Gabiru and the Hiryu drop the airships, Ultima deploys “Nuclear Flame” to incinerate vessels, and Testarossa eradicates entire divisions. The Imperial vanguard of 200,000 tank troops and 40,000 airship personnel is utterly defeated!
Rimuru relocates the capital city into the Labyrinth’s 101st floor. Calgurio leads the main army of over 530,000 troops into the dungeon—but not a single soul survives! The dungeon fields the “Labyrinth Top Ten,” each possessing power comparable to a Demon Lord. Kumara slaughters Kansas using her eight tails, while Apito and Zegion entirely wipe out the elite Imperial guardians.
Bernie and Jiwu, Imperial Single Digit guardians, launch a surprise assault on Rimuru inside the control room. Rimuru discovers that these two “borrowed” their Ultimate Skills from someone else. Rimuru responds by lending his own power to Benimaru and Chloe. Benimaru flips into the offensive to execute Bernie, while Chloe successfully eliminates Jiwu.
The remaining 170,000 Imperial soldiers resolve to fight to the death. Carrera unleashes “Gravity Collapse”, a top-tier nuclear strike magic, generating a pseudo-black hole that compresses the gravitational field and reduces over 80% of the army into dust in a single blow! Following this, Diablo manifests before Calgurio, snapping his fingers to reap the souls of all remaining soldiers. All 940,000 Imperial troops have their souls harvested, marking a 100% flawless victory for Tempest.
Rimuru acquires 240,000 souls to evolve his subordinates into true Demon Lords, granting them the title of “Kings” across 12 individuals: Benimaru, Gobta, Geld, Gabiru, Ranga, Testarossa, Ultima, Carrera, Kumara, Zegion, Adalmann, Shion, and Diablo. Rimuru gains his new title, “Chaos Creator”, permanently shifting the power balance of the world forever.
The truth comes to light: Rudra never intended to simply win the war, but rather to “filter the talented” into Saints to use as pawns against Guy. A massive tables-turn occurs when the three demonesses are defeated by the parallel manifestation of the Scorch Dragon, Velgrynd. Rudra utilizes the Ultimate Skill “Justice King Michael” to defeat Yuuki and bring him under control.
The Pivotal Scene: While Veldora is locked in combat with Velgrynd, the Empire’s Lieutenant Kondo fires a special faster-than-light bullet directly into Veldora, causing the Soul Corridor linking Rimuru and Veldora to fracture. Veldora is stolen away! Confined to an isolated dimension, Rimuru blames himself and plunges into absolute fury. He resolves to fully unleash the immense power he had been holding back, closing with Rimuru entering full-seriousness mode fueled by sheer wrath to reclaim his best friend!
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