Guts, a man who calls himself "The Black Swordsman", looks back upon his days serving as a member of a group of mercenaries. Led by an ambitious, ruthless, and intelligent man named Griffith, together they battle their way into the royal court, and are forced into a fate that changes their lives.

An immortal being takes on the form of a human boy, wandering the earth and experiencing the pains and joys of life throughout his story without end.