"Ambition in the Demon Army" (帝鬼軍のヤボウ Tei Oni-gun no Yabō?) is the twenty-third chapter of the Seraph of the End: Vampire Reign manga series, written by Takaya Kagami and illustrated by Yamato Yamamoto.
Shinoa's squad meets to tell Yu about what happened in Shinjuku and decide where to go from here. Shinoa's squad decides to continue following Guren, making their official policy to take care of their "family".
Later, Kureto and Guren meet, and Kureto asks Guren how did he create so many wielders of the Black Demon Weapons in such a short time, but Guren refuses to say anything on the matter. As they chat, Kureto reveals his plan to first eradicate the vampires of Japan and then dominate the human survivors all across the world, making Japan the center of the world, which Guren considers a childish plan. Kureto says the vampires intend to make a major attack on Tokyo in one month, and orders Guren to go on a suicide mission with 100 soldiers to Nagoya to eliminate some noble vampires while Kureto leads the main army elsewhere.
In Kyoto, Mikaela, Lacus, and René prepare for deployment to Nagoya on the same day Shinoa's squad is ordered to take down Nagoya.
Yu wakes up. That was the first night he slept without having any nightmares since receiving Asuramaru. He meets with Kimizuki, who lives in the apartment next door, and they meet Yoichi on the way to their meeting with the girls.
The three boys arrive at the barracks and, hearing screaming, they rush into Shinoa's room. Mitsuba had added sake to the omelet she was cooking and was running back and forth across the room with a flaming omelet in her pan.
Kimizuki takes over cooking breakfast, and upon Yu expressing his impatience, Shinoa begins the meeting. She tells Yu he was subjected to an experiment that made him lose control and try to kill her. She says they must decide whether Guren is only using them or if he is their ally. She states he is probably picking a fight with the higher-ups or else has a bigger plan in the works.
On the streets of Shinjuku, Guren meets with Kureto. Chained, starving vampires leap at Guren while Kureto watches. Guren questions Kureto's actions, and Kureto informs him that he is testing if he can force the vampires into becoming demons to make Cursed Gear more quickly. However, the few who do become demons are much weaker than even the replicas of the stronger weapons. Kureto orders them slaughtered. Guren says he followed orders to come alone because he knows Kureto will not kill him so long as he is useful.
Kureto asks how Guren created three successful black demon candidates at once. Guren says it was chance, but Kureto calls him out on his obvious lie. Every single person capable of bearing a black demon weapon has been part of a human experiment at one point, but even then the chance of successfully bearing the weapon is slim. He is happy so many bearers were created, but he requests that Guren share any more successful experiments with the army. Kureto then asks Guren if he is planning a coup, and Guren answers that he is not. Kureto calls Guren weak because he cannot betray his friends or sever his emotional attachments, and he tells Guren that he is unworthy of leading. He adds that this is why he trusts Guren. Guren asks which hostage Kureto is going to use this time, but Kureto says he was too busy rebuilding the city to bring one.
Kureto states that anyone who sacrifices another for greed with no ambition is evil. He claims he will rebuild the the world. The first things the vampire did was to destroy all internet connections, cell towers, and other communication lines to keep human countries from getting into contact with one another. Guren asks if re-establishing international communication is Kureto's first goal, but Kureto explains that he will actually first eradicate the vampires in Japan. Then, he will crush any surviving human organizations and essentially conquer the world. Guren calls him out for acting like a kid, and Kureto says it sounds cool. He insists that Guren join him if his ambition is any less than Kureto's.
From within him, Mahiru whispers to Guren, telling him to continue following her instead.
Guren answers that he is already following Kureto, and he would be dead if he were not.
Kureto reveals that the vampires use weak and simple strategies because they underestimate humanity. Vampire enclaves do not get along or share information, and the nobility is responsible for keeping the society under control. By eliminating them, the remaining vampires will fall apart. He says there are 25 vampire nobles in Japan, and claims to know where every single one of them is. His information is gathered from child spies he sends into vampire cities, which Ferid seems a little too happy about.
While Ferid is strolling down the streets of Sanguinem and checks out the cute children nearby (the children fleeing at the site of him), Dai's friend from the previous chapter approaches Ferid. He heard that letting Ferid drink his blood would get him something in return, and Ferid asks him if Mika was the one who told him that.
Kureto explains that vampires do not bother to remember the faces of humans because they are too cocky and only see humans as brainless livestock.
Kureto assigns Guren a suicide mission. Before the vampires bring down their army on Tokyo in a month's time, Guren must launch a preemptive strike with a force of 100 soldiers and his three black demon wielders. He will attack Nagoya, wipe out the vampire nobles, and conquer their base. In the meantime, Kureto will lead the rest of the army elsewhere. He is using Guren as a distraction, although killing off nobles will help their cause as well. Kureto declares that if Guren follows orders, he will show Guren a world where the humans make the vampires into cattle.
Back in Shinoa's apartment, Shinoa lists Guren and the Hīragi family as being the largest factions fighting for power in the Demon Army. Yu says he wants to follow Guren since Guren saved his life, and says he will follow Guren even if he betrays him because he is family. Everyone agrees. Shinoa makes their official policy "family takes care of family."
In Kyoto, Mikaela, Lacus, and Rene are wearing their new uniforms. They have been ordered to deploy to Nagoya with the the rest of the army to eliminate humanity in the northeast. That same afternoon, Guren gives orders to take Nagoya.
List of characters in order of appearance: