The World of Blood Legacy

Blood Vessel World 「血脈のセカイ, Kechimyaku no Sekai」 is the first chapter of the Owari no Seraph manga.

Summary
At the beginning of the chapter, it is stated that an unknown virus had appeared and only children had survived but they were enslaved by vampires who appeared from the 'bowels of the earth'.

The setting was 2016, of the vampire calendar, in the underground city of Sanguinem. Yūichirō and Mikaela were first introduced as Yūichirō had shouted for his friend to tell him that in the book that he was reading, 'Memoirs of those who roam the Darkness', a vampire dies if you smash their heads. Mikaela didn't bother listening as he was thinking. Yūichirō kept on telling him facts about ways to kill a vampire but Mikaela still didn't want to hear. Yūichirō also announced to him that he wanted to kill the vampires when he was older but Mikaela argued back that it would be impossible because vampires were stronger than humans. Yūichirō tried to argue back but couldn't as he was injected with a syringe and had blood taken from his neck. Mikaela had his blood taken too and the both stayed silent in their seats for a bit.

After the children were let out to talk and have a little fun, Yūichirō started complaining about the vampires taking blood from him, treating him like a livestock, which he was. He then told Mikaela that they should start a rebellion against the vampires but Mikaela found it ridiculous and said that he either dreamed too much or read too much manga. Yūichirō denied reading manga aloud, as well as the 'killing vampires' part too, which Mikaela told him to stop. And behind the vampires' backs, Yūichirō declared he'd kill them and lied about doing 100 push-ups every day. Mikaela then told him that he couldn't win with physical strength and that he needed to think, which Yūichirō couldn't do.

When Felid arrived, Mikaela ran over to him and greeted him, which he did the same. Felid then had invited him over to his house to which Mikaela had accepted. Then Felid had left with his vampire bodyguards behind him.

Yūichirō was annoyed with the fact that Mikaela let a vampire (Felid) drink his blood of his own free will. But Mikaela had argued back that he used his blood to get a better reward of food and other luxuries. Yūichirō felt more annoyed and had punched him, walking away and leaving Mikaela worried of him.

Later that night, Akane visited Yūichirō and asked why he was mad because they were family and she was worried. Yūichirō responded that he had no family but Akane still told him because the Director said that they, the Hyakuya kids, 'all belong to the same family'. A flashback was then set about 4 years into the past (2012) when Yūichirō had first joined the orphanage. He was first introduced to a lively Mikaela who introduced himself. Yūichirō turned his head away and Mikaela stubbornly took his hand and shook it. Yūichirō screamed, demanding what he was doing and being sarcastic about a challenge to who is the leader. Mikaela then replied with him being the leader that then made Yūichirō scream as if he was foolish. Yūichirō was beaten up by Mikaela who still had a smiling face on. He welcomed Yūichirō with open arms into the family. Yūichirō said it was ridiculous because of his past with his father and mother. After hearing that, Mikaela had shared his past too, which was more abusive than Yūichirō's and then the other children at the orphanage shared their stories too. They all ran over to Yūichirō to celebrate him in becoming a brother to the family. After a peaceful moment, the Director collapsed as blood ran down her nose and mouth. The children ran over to her and Yūichirō and Mikaela heard a car crash outside. The streets and buildings were burning and walking down a road were vampires. Kururu was leading the vampires and announced the virus that was spreading amongst the humans. Mikaela then ran back to the Director to aid her back to health and told Yūichirō to look after the children.

The story is then taken back to 2016 with Akane explaining that the vampires took them to their underground world. She then told Yuichiro that he should come down for dinner as they were waiting for him. When he got down, he was shocked to know that Mikaela had been able to give them rice to eat as they have always had trash food. During the night, Mikaela walked inside the room where everyone was sleeping and found that Yuichiro was still awake.

Chapter Notes

 * Yūichirō Hyakuya and Mikaela Hyakuya are introduced.
 * According to a book:
 * Vampires can be killed if you shot them on the head or if you remove their armband device they can be killed by ultrasonic waves.
 * The physical strength of a Vampire is 7 times that of a human.
 * Vampires allow the kids to live in exchange of their blood.
 * Michaela lets Felid drink his blood and in exchange he buys him anything he wants.
 * The kids met each other four years ago in the Hyakuya Orphanage.
 * Yūichirō ended up in the orphanage because his father tried to kill him and his mother spread a rumor that he is the son of a demon, then she lost her mind and she killed herself. Mikaela ended up there because he was abused by his parents and then dropped out of a car and  taken in by the orphanage.
 * Blood suddenly began to pour from the directors mouth and nose leading to her death.
 * Vampires attacked the city and a lethal virus spread among humans who were older than 13.
 * The troops were under the direct command of the third founder Kururu Tepes.
 * It was announced by the vampires that from that day on the children would be in their charge.
 * Michaela steals a gun and a map showing the way outside of the underground world from Felid.
 * The kids attempt to escape but Felid was waiting for them.
 * Felid murders all the children except Yuichiro who shot him in the head with a gun.
 * Yūichirō escapes from the underground world and reaches the outside world alone. There he finds a man with two women who asks him if he will help them exterminate the vampire race, Yuichiro accepts.