Tatsumi is a fighter who, accompanied by his two childhood friends, sets off to the Capital in search of a way to make money to assist his poverty-stricken village. After being separated from his friends in a bandit attack, Tatsumi unsuccessfully attempts to enlist in the army and is swindled out of his money in the Capital. He is taken in by a noble family, but when an assassin group called Night Raid attacks, he learns that his noble hosts actually intended to torture and kill him as they had done with his friends.

As a result, he joins Night Raid, which consists of the swordswoman Akame, the beastly fighter Leone, the sniper girl Mine, the scissor-wielding Sheele, the string manipulator Lubbock, the armored warrior Bulat, and their leader Najenda, a former general of the imperial army. Night Raid is also part of the revolutionary forces assembled to overthrow the prime minister Honest who is manipulating the young emperor for his personal gain despite the rest of the nation falling to poverty and strife.

The members of Night Raid carry Teigu (帝具, anime: Imperial Arms), unique weaponry created 900 years ago out of extremely rare materials as well as legendary animals called Danger Beasts (危険種, kikenshu). The power of the Teigu is so overwhelming that it is said that when two Teigu users fight each other, one of them is bound to die.

Although Night Raid successfully assassinate some of Honest's cohorts, they lose Sheele during a fight against capital garrison member Seryu and then Bulat when Honest recruits the Empire's sadist general Esdeath and her Three Beasts. Tatsumi receives Bulat's Teigu, Incursio, as a result while Esdeath replaced her slain subordinates with a group of Teigu-using warriors called the Jaegers. Night Raid, along with new recruits Susanoo (a humanoid Teigu owned by Najenda) and Chelsea, fight the Jaegers with Seryu, Wave, and Akame's younger sister Kurome among its ranks. Over time, the two factions gradually lose some of their members.

When the revolution gains momentum, Honest forms a new secret police force, the Wild Hunt, led by his own son, Syura. But Wild Hunt heavily abuses its authority by killing innocent civilians for their own plans, antagonizing both the Jaegars and Night Raid. After a battle between Wild Hunt and the Jaegers, with casualties from both sides, Esdeath blackmails Honest into dissolving the rest of Wild Hunt. Syura is killed by Lubbock after he captures both him and Tatsumi. Lubbock is killed while attempting to escape, and Tatsumi is sentenced to death despite Esdeath's attempts to save his life. The remaining Night Raid members attack the execution site to rescue Tatsumi while being pursued by the imperial general Budo, who Mine manages to kill at the cost of her Teigu while falling into a coma.

Due to the stress he experienced while escaping the execution site, Tatsumi caused Incrusio to transform. It would be revealed that Tatsumi caused the Danger Beast which Incrusio was created from, Tyrant, to awaken with the doctor predicting that Tastumi can use his Teigu a few more times left before it fully fuses onto his body and consumes him. As this occurs, Night Raid confronts the last members of Wild Hunt and finish them off, with Akame taking out big generals on the Empire's side. Akame leaves a message to Wave that she and Kurome intend to settle things as they promised each other. After his attempt to convince Kurome not to get through with it, fighting his way through Tatsumi, Wave manages to stop the sisters' duel and destroys Kurome's Teigu. With this, Wave and Kurome fake their deaths as they run off to start a new life together.

After hearing the news of the remaining Jaegers' deaths, Esdeath resumes her duties as general to hold off the Revolutionary Army when they begin a siege on the capital to remove Honest from power. As a last resort, Honest convinces the emperor himself to join the fight with his family's Teigu. After the remaining Night Raid members assassinated those in the government who have been pulling the strings behind the stage, only Honest and Esdeath are their remaining targets. However, Honest rigged the emperor's Teigu to go berserk.

To confront the emperor's Teigu, Tatsumi uses his last transformation to defeat it with Wave's help while changing into Tyrant. Before being fully consumed, Tatsumi asks Akame to kill him before he loses control and kills everyone. She does so during her battle with Esdeath, later revealed to have only killed the Danger Beast's soul so Tatsumi can live, managing to defeat the general at the cost of her own sword. Esdeath acknowledges her loss and uses her power to commit suicide while regretting that she never got Tatsumi to return her feelings. As the final battle unfolded, Honest attempted to flee before being mortally wounded by Leone after he fatally wounded her and she fused with the remains of her Teigu to give her enough time to capture him so the Revolutionary War can fully end.

In the year 1024 of the Imperial reign, Tatsumi and his childhood friends Ieyasu and Sayo set off together from their home village with dreams of earning fame and money. Along the way, the trio are separated when attacked by bandits. Later Tatsumi saves a caravan from a first-class Danger Beast, dispatching it with ease, displaying his talent for combat.

Tatsumi arrives at the capital

Tatsumi arrives at the capital

Tatsumi arrives at the capital and attempts to enlist in the Imperial army, but is turned away due to the flood of applicants due to a recession. Sitting outside the recruitment office, wondering what to do next, A beautiful woman appears before Tatsumi offering to help him in exchange to treating her to a meal. The woman tells Tatsumi that with connections and cash payment, he would be able to get into the Imperial army, and he gives her his bag of savings. The woman leaves with Tatsumi's money, promising to use it to secure him a position, but after hours of waiting, Tatsumi realizes he was tricked.

A dejected and broke Tatsumi sits beside the road, planning to sleep there, and is found by a wealthy young woman named Aria, who offers him a place to stay. Tatsumi is distrustful at first, but accepts her offer. The next day, Tatsumi is told by one of Aria's bodyguards of the child Emperor, and his Prime Minister, who is corrupting the once great Empire. He is also told of the assassins called "Night Raid" who oppose the Empire.

Later that night, Tatsumi awakes sensing bloodlust. He runs out of his room and witnesses Night Raid for the first time. The family's bodyguards attempt to defend the mansion but are cut down one by one. Tatsumi finds Aria and attempts to guard her when a female assassin arrives, targeting her.

Akame stabs Tatsumi

Akame stabs Tatsumi

The female assassin warns Tatsumi that she will kill him if he gets in her way, but he refuses to stand down. The woman who took Tatsumi's money previously shows up and watches as Tatsumi and the female assassin cross swords. Tatsumi then appears to be stabbed, but was saved by the idol that the Village Chief gave him before embarking on his journey. The female assassin prepares to attack him once again but is stopped by the woman who took Tatsumi's money, who is revealed to be a member of Night Raid as well.

Tatsumi kills Aria

Tatsumi slays Aria

She proceeds to reveal to Tatsumi the true nature of Aria and her family's as sadists who kill innocent people, kicking in the door of their torture room. Tatsumi is shocked to find Sayo among the mutilated captives, and a barely-alive Ieyasu in a cage, who tells him that Aria tortured Sayo to death. Aria admits to the crime and reveals her views of peasants being used as cattle and how she has the right to use them. As Akame prepares to kill her, Tatsumi stops her and slays Aria himself. After killing Aria, Tatsumi frees Ieyasu from his cage and watches Ieyasu succumbing to the Lubora disease, which Aria's mother infected him with. Saddened by the lost of his two best friends, Leone (the con-girl) and Akame (female assassin) discuss taking Tatsumi back to Night Raid's hideout with them much to Tatsumi's surprise and reluctance. Leone then grabs a reluctant Tatsumi and they head to where the rest of Night Raid is waiting for them.The other Night Raiders ask who Tatsumi is, and Leone replies "one of us". Tatsumi is confused, but is forced to come along, being carried by Night Raid member Bulat. Night Raid (with Tatsumi) then head back to their hideout.

A flashback of Tatsumi, Sayo and Ieyasu appeared with the three of them declaring that they'd save their village. Then the present came, with Tatsumi looking down at his two friends' graves. At that moment, Leone appeared, asking him if he made a decision on whether to join Night Raid or not. She then insists - more like forces - on showing him around the hideout.

The first person the two meet up within the hideout was Sheele, who was reading a book that said '100 ways to fix airheadedness'. Leone asks her to say some warm words to him but instead, she said a threatening sentence. At that moment, Mine barges in and exclaimed why Leone had let Tatsumi in the hideout. She responds with Tatsumi being apart of the team which Mine counters with Tatsumi having to have the boss's (Najenda) approval. She also states that Tatsumi is not qualified to work with professionals like them, judging from the way he looks. Tatsumi found that insulting and called her a punk, which she ignored.

Then Leone showed Tatsumi the training ground where they found Bulat. At first, he didn't know who the man with the spear was but when Bulat told him that he was the armored guy, Tatsumi understood. They shook hands. Leone then told Tatsumi that Bulat was gay, to which Bulat told her that Tatsumi would misunderstand. But Tatsumi was freaking out since Bulat didn't deny that he was a homo.

Then it appears with Lubbock hiding by the bushes, hoping to see Leone ***** at the hot spring. He was then caught by Leone and was threatened to have his fingers and arm broken. She then introduces Lubbock to Tatsumi. Straight after, the two head to the riverbed where Akame was.

Once they arrived, Tatsumi was shocked to see that Akame had caught an Evil Bird and was eating it. Akame gave Leone a piece of the meat but didn't for Tatsumi because he wasn't one of them yet. And surprising both Leone and Tatsumi, they found that Najenda was there too. Leone was punished for going over the operation by Najenda. She then asked who Tatsumi was and Leone responded with her recommending her to accept him into the group