If you're looking for manga similar to Blackguard, you might like these titles.
Includes the following chapters:
In a ruined city, Takeru comes across a suicidal young girl named Konoha. She's deathless, and she's being used as a guinea pig by a cruel organization. Seeing no meaning to her life, she fled her captors to seek a way to end it. Takeru has a lot in common with Konoha-- he's also deathless. He's made a life for himself, though, locating people by contract. After he rescues her from her pursuers, he convinces her to continue living. Maybe she'll be able to find a purpose, as she and Takeru face the future together.
After a major natural disaster, earth is slowly transforming into a desert in which mankind tries to survive. Water becomes a precious resource and the center of political intrigues. In the middle of this, a young boy, member of a gang, encounters a beautiful girl who's a merciless warrior and holder of the key to the salvage of humanity.
En has no prospects as a child of the slums—he ekes out a living by selling the scrap cyborg augmentations he scavenges to anyone who will buy. But when he's forced to go through some unethical experimentation, he transforms—making him eligible to become a fighter in the only thing that matters in this bleak world: The Rokudo Tournament!
In the middle of a long war, scientists invented a drug that transforms the fear of death into pleasure, making it possible for school girls to fight alongside men. In this world of death, drugs, and rampant sex, one girl still dreams of true love. Will she find her romantic, happy ending?
Rei is a ruthless man who travels throughout the world in search of a certain someone. But he was not always ruthless and without compassion--both his search and his anger are driven by vengeance. The one who stripped Rei's humanity from him is the one Rei must find and destroy, despite any and all barriers. Rei will only become a normal human being once that vengeance is fulfilled. Until that day, he can only roam the world as a furious lone wolf, a lone wolf who preys on those who oppose him.
The story of two immortal children, beginning at the time in which the everything has ended. The innocent older sister π that loves to rap, and the introverted younger brother Makki that you can always find reading alone.
Includes the following chapters:
Suicide is on the rise for no apparent reason, affecting adults and children alike. All they have in common is accounts in a brutal online game called Dystopia. When tragedy strikes a woman named Hitomi, she soon joins Dystopia and explores its horrors. But when she realizes the game feels a little too real, it’s up to her and a genius hacker named Shunsuke to figure out what’s really causing these deaths.