The blood contract: Rise of crimson blade swordsman

Ran, a weak and exiled bastard child of the powerful Bloodrune family in the continent of Morphy. Lacking any magical talent due to a mysterious internal disease, Ran is discarded by his noble bloodline and forced to survive as a lowly mercenary. Everything changes when he is forced into a sadistic game orchestrated by a grotesque, unkillable demon. After watching his comrades die and tearing off his own arms to survive, Ran is offered a blood contract by the demon—a cursed deal that replaces his heart and grants him access to dark energy and a mysterious crimson sword. In exchange, his soul will be consumed upon death. Now a lone wanderer with unstable power and growing bloodlust, Ran hides his cursed origins and lives among the fringes of society. He arrives at Fafnir Academy, an elite institution that trains the continent's strongest warriors, under the guise of earning a scholarship to survive and gain strength. As he fights to suppress the bloodthirst overtaking him, Ran is drawn into deeper conspiracies involving ancient demons, forgotten wars, and nobles who will stop at nothing to control power. He forms a bond with many women throughout the journey and learns to be human again.