Sora Mitsurugi, the thirteen-year-old heir of the Mitsurugi household, faces a sacred trial to learn his family’s secret phantom blade style. The Mitsurugi family has been entrusted by the emperor with the crucial duty of guarding a demon gate, and this test determines who is worthy of carrying on that legacy. While the seven other pupils his age all pass, Sora alone fails. In an instant, his life crumbles. His father, the master of the phantom blade style, disowns him and casts him out. His best friend mocks him with pitying coins, and his fiancée, Ayaka Azurite, coldly dissolves their engagement, declaring she was only promised to the heir, not to him personally. Left with nothing, a heartbroken Sora visits his mother’s grave before being expelled from the island to survive on his own.

Five years pass. Sora has been surviving as a low-ranking adventurer, nursing his wounds and dreaming of one day earning enough recognition to return and prove his father wrong. However, his fortunes seem to take another turn for the worse when he crosses paths with an adventuring party called the Falcon Blades. In a desperate encounter with a monstrous giant bee known as the Lord of the Flies, the party cruelly betrays Sora. One of its mages shoots him, using him as bait to distract the creature so the rest can escape. Captured and dragged into the monster’s lair, Sora is left for dead. But at his lowest point, he discovers a terrible power within himself. By consuming the larvae of the giant insect, he gains a dark and fearsome ability, transforming into the Soul Eater and acquiring a shadowy scythe as his weapon.

Reborn not as a weak exile but as the Soul Eater, Sora swears a meticulous and merciless revenge against all who have wronged him. His primary targets are the members of the Falcon Blades, the party that betrayed him so callously. He begins to systematically hunt them down, starting with the warrior priestess Iria. Using cunning and his new powers, he heads to her ailing home village of Merte to lay the groundwork for his plan. One by one, he forces his former comrades into servitude, turning the tools of his betrayal into the instruments of his vengeance.

However, the world is larger than Sora’s personal vendetta. His actions draw him into a geopolitical struggle between the small Kanaria Kingdom and the expansionist Ad Astra Empire. The Empire has been rising at an unnatural speed, fueled by the power of heart equipment wielders, soul-armor users like Sora from the very鬼之岛 (Oni Island) that cast him out. When the Dragonote公爵家 (Ducal House of Dragonote), the kingdom’s proud dragon-riding protectors, are humiliated by the Empire’s schemes, Sora finds himself intervening. He uses his Soul Eater ability to break a curse on the duke’s daughter, Claudia, which leads to a direct confrontation with an imperial assassin, the monstrous monk Jininbo. As Sora navigates these treacherous political waters, his quest for personal revenge becomes entangled with the fate of kingdoms, forcing him to confront the family that abandoned him and the empire that seeks to exploit his kin’s power for conquest.