The World of Blood Legacy

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

Summary
In 2012, the world allegedly comes to an end at the hands of a human-made virus, ravaging the global populace and leaving only children untouched. It is at this time that vampires emerge from the recesses of the earth, likely followed by age-old horrors of the dark thought only to be myth. The vampires sweep the earth and claim it in a single violent stroke, subjugating the remnants of humanity and leading them beneath the surface to safety. This "protection" comes at the price of donating blood to their captors, which leads us to the beginning of this story.

Yuichiro Hyakuya is a member of the vampires' "livestock" in the underground city of Sanguinem, just beneath Kyoto. He lives there with the orphanage he was inducted into, just before the viral outbreak 4 years earlier. Among the children is another boy the same age as Yu, named Mikaela Hyakuya (nicknamed Mika) and a girl named Akane. These three watch after the rest of the children, who are too young to fend for themselves. The boys are polar opposites in personality. Yu is a brash, impatient loner while Mika is bright, intelligent, smiling brightly and making all the children feel safe and protected around him.

One day, Yu muses about having to give blood to his captors and brags about how he plans to slay them all someday. He and Mika run into a vampire not wearing a hood: a Noble by the name of Ferid Bathory. Mika gleefully calls after Ferid and runs to him without a hint of distrust, with Yu watching as the vampire caressed his cheek. Mika agrees to meet Ferid at his mansion later on, and Yu learns his best friend had been meeting illicitly with the vampires he so loathed. Mika tries to explain that doing this entitled him to certain advantages, but Yu refused to listen and stormed off.

That evening, the orphanage children enjoy curry thanks to Mika's efforts. Mika does not return until later that night, and Yu asks him what he had to do to get that curry. Yu says that he will sell his blood instead next time. Mika rejects his offer, and Yu scolds him for trying to do everything himself. Yu presses the issue, and Mika starts crying. A moment later, he claims he was just kidding and pulls out a gun and map. The two wake up the other children, setting off to escape Sanguinem that very night.

The children make it to the gates of the city, but Ferid Bathory was waiting for them. Ferid slaughters the children in front of Yu and Mika for the sadistic pleasure of crushing his Mika's spirit. The two fight back, but Mika is mortally wounded. Yu manages to shoot Ferid in the head while he is distracted by ripping Mika's arm off. Yu is surrounded by the lifeless stares of dead children and Mika, who is bleeding out. At Mika's urging, Yu runs out through the gates as the only survivor of the Hyakuya Orphanage. He runs into a with a platoon of vampire-hunting human soldiers led by a man named Guren Ichinose, and thus Yu's quest for revenge against a race of nightwalkers begins in earnest.

Chapter Notes

 * Yūichirō Hyakuya and Mikaela Hyakuya are introduced.
 * According to a book:
 * Vampires can be killed if you shoot them on the head or if you remove their armband device as 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.
 * Mikaela lets Ferid Bathory 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 kicked out of a moving car by his abusive parents and was taken in by the orphanage.
 * The virus hit the Hyakuya Orphanage, which the Director contracted. 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 vampire troops were under the direct command of the third founder Krul Tepes.
 * It was announced by the vampires that from that day on the children would be in their charge.
 * Mikaela steals a gun and a map showing the way outside of the underground world from Ferid.
 * The kids attempt to escape but Ferid was waiting for them.
 * Ferid murders all the children except Yūichirō 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, Yūichirō accepts.