I'm the Evil Lord of an Intergalactic Empire!

As Liam Sera Banfield leads his fleet into battle, he recalls the collapse of his past life as a salaryman putting in long hours at an abusive workplace for his wife Mika and daughter Kanami. He discovers Mika has cheated on him with a man that Kanami loves more, then loses his job after being falsely accused of embezzlement.

Mika divorces him and takes full custody of Kanami, and he is forced to work as a laborer just to pay child support. As he lays dying alone of an illness he cannot afford to treat, an entity calling himself the Guide appears and reveals that Mika had Kanami with his own boss, who also framed him for embezzlement.

The Guide offers the dying man a choice of worlds to reincarnate in, and he chooses a sci-fi fantasy universe, vowing to live an evil and self-absorbed life.

Liam awakens on his family's planet Hydra on his fifth birthday, where his parents gift him a customized android "doll" before bequeathing their entire domain to him so they can retire to a comfortable life on the Imperial Capital planet.

Back on Earth, the Guide reveals that he had manipulated Liam's former boss and Mika to fatally exacerbate his misery before having the latter arrested as they have dinner in a fancy restaurant, devastating Mika. The Guide excitedly expects to feed off of Liam's misery in his new life as people in the new universe live significantly longer. As he steps into a portal to the new universe, a glowing puppy appears by Liam's side before following the Guide through.

The doll arrives at Liam's mansion, and he names her Amagi. While he tries to physically enjoy her company, his butler Brian informs him that people in this galaxy live much longer lives, and that possessing artificial intelligence is frowned upon due to a previous AI revolt nearly destroying human civilization. He then informs Liam that his parents have squandered the prosperity built by his great-grandfather Alistair and abandoned their responsibility by making him the head of the family.

Liam realizes he is now in a similar situation as his past life, but this time he has control and others he can trust to help him. He implants his own interpretation of the Three Laws of Robotics into Amagi's memory to ensure her trust and requests her to start bringing the domain's finances to order while he enters a special stasis capsule to accelerate his formal education.

Elsewhere, Princess Christiana Rosebreia begins battle with a fleet of space pirates.

Liam exits the education capsule after two years to find that Amagi has stabilized the domain's finances, although there is still much to be done. He is introduced to the Banfields' fleet and their corps of mobile knights, and is inspired to learn to fight in one of their mecha suits.

Christiana responds to an offer of peace from pirate Captain Goaz, but realizes too late that he had bribed her supposed allies to betray her and allow Goaz to invade her home planet Mysteria.

Liam and Amagi hire the ronin Yasushi to teach him an allegedly secret martial art called the Way of the Flash, unaware that Yasushi is actually a con artist. Nevertheless, Liam genuinely dedicates to training, even paying Yasushi extra to stay on further.

Liam identifies an official embezzling funds and is almost inspired to do so himself before Amagi informs him he had tried to cover it up by frame a subordinate. This triggers memories of his own betrayal, causing him to decapitate the official with his sword. Amagi convinces Liam to replace enough officials with other AI maids to ease the transition to better governance, and the people of his realm start seeing genuine improvements to their standard of living.

Afraid of his secret being exposed Yasushi claims Liam should not rely on a mecha's autopilot, but with an older model with much more difficult manual controls. The commander of the mobile knights suggests Liam use Alistair's personal mecha.

Liam decides to repair his great grandfather Alistair's robot, the Avid. Amagi starts to suspect Yasushi is a fraud. Liam summons Imperial Engineer Lieutenant Nias Carlin to repair Avid. Yasushi becomes obsessed with Nias but she ignores him completely. Yasushi vents his frustration by making Liam's fake training even more difficult. Goaz adds Christiana to his collection; beautiful girls he takes pleasure in slowly mutilating to death. Nias finishes restoring Avid as a fully manual robot with no AI. As its movement requires mental focus Avid ends up performing lewd movements when Liam is distracted by Nias' breasts. Yasushi is so jealous he makes Liam's training even harder. Liam becomes depressed when he makes no progress in the Way of the Flash, so Amagi tries to suggest Yasushi is untrustworthy. Liam misinterprets this as his needing to train even harder and after several more years he succeeds in using magic to, in fact, create the Way of the Flash which Yasushi had only faked with trickery. Despite his terror at Liam's impossible skill Yasushi once again convinces Liam he needs even more training, ensuring his employment for a while longer. Pirates target one of Liam's mining planets, so he decides to test his skills in battle by piloting Avid against them. Using the Way of the Flash Liam destroys 30% of their fleet, captures 10% and allows 60% to escape.

Goaz decides to execute his cowardly invasion fleet. Amagi reports that of Liam's 10,000 ships only 3000 are operational, so Liam decides to purchase new ones. Elsewhere, Nias struggles to sell her new combat ships, since the Empire's generals insist on buying ships from her rival Lieutenant Eulisia Moriselle, whose ships are built for luxury. She suddenly realises her ships might appeal to Liam. Guide decides to visit Liam, certain his negative emotions would have built up from his parents' debt and a fraudulent sword master. However, he discovers Liam has restored Hydra's economy and become a master swordsman. Liam decides to buy the second hand ships the Empire is replacing with the luxury ships, so Guide ensures the crews are made up of honourable officers that will not tolerate evil men like Liam and rebel against him. Nias visits Yasushi to ask his advice on approaching Liam. Yasushi believes she is seducing him and shares his clothing fetish with her. Believing he is referring to Liam, Nias attends their meeting wearing sexy panties, a skirt and stockings. Liam, who recalls his ex-wife dressing like that, is unimpressed. Despite having agreed to buy the Empire's ships he also agrees to buy Nias' ships so she will stop exposing herself. Brian worries Liam might never marry a real woman, but becomes convinced there is hope with Nias.

Liam takes delivery of his new ships, paid for in part by allowing Nias to acquire some of the captured pirate fleet for study. Yasushi is certain Liam is seducing Nias and swears revenge. While touring one of the captured pirate ships, the golden dog appears and leads Liam to its navigation room, where he and Amagi deduce that the pirates travel to and from a planetoid that Liam calls Treasure Island.

Goaz decides to finish the Banfields and leads his fleet to a warp gate whose staff he has bribed to grant them passage. At the opposite gate, Liam is denied entry by the gate's manager due to his family's bad credit history. Liam personally enters the gate facility on his side but fails to convince the manager to let his fleet through.

The manager then excuses himself to accept Goaz's bribe and let the pirate fleet through before taking the gate control crew to break. The golden dog leads Liam to the empty control room where he notices the gate is open but set to exit on his side. Thinking the manager took pity on him to open the gate in the first place, he reverses the warp gate's direction while Goaz is still traversing it, inadvertently ejecting the pirates into the path of a large Imperial fleet on training.

Returning to his flagship as Nias has offered to pay the toll as repayment for the captured pirate ships, Liam takes his fleet through the gate toward Treasure Island.

A letterboxed flashback shows Goaz and his pirates destroying Christiana's home planet Mysteria and the subsequent horrors inflicted on her and her surviving crew by Goaz and his mad doctor, which took place many years before Liam's arrival.

Arriving at the Treasure Island planetoid and quickly defeating the pirates stationed there, the golden dog appears again and guides Liam to the mad doctor, who then shows off his gruesomely mutilated specimens, including Christiana. Horrified at seeing someone treated worse than he was in his previous life, Liam summarily executes the doctor and orders Goaz's treasure be used to restore his victims' bodies to normal.

After returning to Hydra, Nias charms Liam into purchasing even more battleships with the remainder of the treasure. Overhearing Nias' jubilation, an envious Yasushi tries to subject Liam to more torture using drones, but Liam still genuinely believes he is training and generates a magical shield that destroys the drones.

Realizing that Liam is now actually skilled enough to figure out he is being scammed, Yasushi declares him a master and flees. Liam loudly proclaims his thanks to the Guide for bringing him to a universe where he is finally prospering - unknowingly much to the Guide's chagrin.

Liam decides to increase his evil reputation by amassing more money and forming a harem. He resolves his personal money issues by accepting bribes in gold - despite gold's relative lack of value in his new universe.

Forming a harem proves even more difficult for Liam: as his star system's ruler he is already expected to have a harem larger than even his wildest fantasies in order to produce an heir, and his desire to be an evil lord seizing any woman he wants cannot happen when he is so beloved that women willingly apply to join.

He decides to visit the city to try to gather a harem but is almost immediately repulsed by the fashion trends of the universe's women. When budget constraints prevent him from hiring designers and models to institute his preferred fashion choices, he ends up settling for working with the women already hired to work in his castle.

Meanwhile, Christiana awakens in hospital to find her body restored to its original form. When the attending doctor tells her that Liam funded the hospital and its staff, Christiana vows to repay her savior.

Enraged at Liam's prosperity and popularity among his people and soldiers, the Guide decides to get more directly involved in the universe in order to extract the negative emotions needed to sustain him.

Yasushi is shocked to find his name permanently associated with Liam, who still truly believes that Yasushi was an authentic master. In his mansion, Liam laments even mealtimes are boring as they feel too civilized for a gluttonous evil lord. Amagi suggests various guests for him, but this merely upsets him that Amagi, being an AI, does not get jealous of other women.

Meanwhile, Liam's other AI maids grow restless as just cleaning his mansion leaves them bored most of the time. They are also confused that Amagi forbids them from being too close to Liam in case it affects his reputation, even deleting their memories of social interactions despite being sexually intimate with Liam herself.

After escaping the Imperial fleet, Goaz is persuaded by the Guide to avenge himself on Liam and invades his star system. As Liam, Amagi and his advisors debate a course of action, the Guide then stops time and encourages Liam to take down the pirates for enough money to clear the family debt. When time resumes, Liam declares his intention to fight.

Liam grows restless after three days without combat, as it turns out war in space between thousands of ships hundreds of miles apart requires considerable strategy before the fighting can even begin. Goaz suddenly sacrifices 500 ships to disrupt Liam's formation then loses even more ships to bombs Liam concealed with magic, but he forces his way through with sheer numbers while hiding his flagship behind force-fields. Brian urges Liam to do the same with his flagship, sacrificing his front line ships in the hope the delay will allow Imperial reinforcements to arrive. In a rousing speech Liam refuses to let Goaz take a single ship from him and flies out on Avid. With Liam no longer aboard the flagship Amagi is able to move it to the front lines and use its more powerful cannons and armour. Liam's knights follow him into battle despite being heavily outnumbered. Avid's right arm starts to break down due to Liam's repeated use of the Way of the Flash and Amagi calculates their chances have dropped from 4% to 1.2%. Liam's sword shatters but he is saved from certain death by Christiana in her new robot Nevan, provided by Eulisia. Liam summons a new sword and unleashes a massive strike that wipes out over half of Goaz' remaining fleet, increasing their chances to 83%. With victory in sight Liam approaches Goaz' flagship.

With Amagi leading his fleet and a vengeance-obsessed Christiana assisting him on the frontline, Liam finally punches through Goaz's lines and reaches his personal flagship. Goaz attempts to flee, but Liam disables the ship and breaks in.

Now desperate to inflict misery on Liam to feed off of, the Guide personally intervenes and grants Goaz superhuman strength and hardened skin to defeat Liam.

The glowing puppy - which Liam recognizes as a pet from his previous life - leads Liam to a golden cube that Goaz dropped, and then to a hidden room full of antiques, where he takes an ornate katana as a trophy. Goaz appears and Liam breaks his sword against Goaz's skin, forcing him to use the katana instead.

The katana easily dismembers Goaz. When informed that the bounty does not increase if Goaz is brought in alive, Liam decapitates him amidst his pleas for mercy. He returns to his flagship where he tells Amagi he was not expecting such an anticlimatic end to the battle.

As Nias, Christiana and Eulisia try to fete favors from Liam, he is informed that he will be commended for his victory at a celebration on the Imperial capital planet.

He is met there by his parents and grandparents who want to share in his success, but Liam angrily banishes them before telling Amagi to slightly raise their allowance to keep them quiet.

The Guide tries manipulating the family's resentment to convince them to depose Liam and seize his wealth before having him assassinated, but the glowing dog leads Amagi to overhear their plot. She informs the Lord Chancellor who then refuses the family's request, adding that Liam's reputation and value to the Empire means that any harm that befalls him will be reflected on his family.

As the celebration ends, Amagi tells him she will resign as he is about to come of age, but more importantly to prevent his enemies from using the social stigma around AI as leverage. Liam convinces her to stay as their emotional bond is strong enough that separating would only bring harm to both of them in violation of the Three Laws.

Liam and Amagi return to Hydra, and he excitedly declares his gratitude to the Guide, overwhelming the Guide to nausea with positive emotion.