Shogen

In the Heian era, a King with royal blood has his elite samurai and shinobi slaughter everyone without it. Shogen, a non-royal born with a demon curse, becomes the greatest samurai alive and starts a war against the royals. The King kills him in a duel, and the demon passes into his newborn son while his wife dies of grief. Nineteen years later, that son, Shigen, is the village’s worst samurai. When the King’s guards kill the old woman who raised him, he takes up his father’s sword and refuses the demon’s offer of power. He leaves to train and then to kill every royal, ending with the King. — Description from novelcodex.orgFull novel: Shogen — read the rest free on N​o⁠v​e⁠l​C⁠o​d⁠e​x⁠.​o⁠r​g⁠