Arthur Pendragon, the second prince of Britain, is executed by guillotine during a violent revolution fueled by oppressive taxes and noble tyranny. In his final moments, he bitterly regrets his ignorance of the suffering around him. Yet when he next opens his eyes, he finds himself back in his royal bedchamber five years earlier, his body restored to its teenage form and his magical healing abilities intact. Desperate to avoid the same fate, Arthur soon discovers that performing acts of kindness with his unique healing skill triggers a mysterious system that awards Good Deed Points and alters the course of the future. A strange diary also appears, recording the exact chain of events that previously led to his beheading, allowing him to track how his actions change what lies ahead.

Driven solely by survival instinct, Arthur embarks on a frantic campaign to win favor with everyone around him, from lowly maids to the resentful commoners who will one day rise against the crown. His self-serving efforts, however, are consistently misunderstood as genuine benevolence, earning him admiration and loyalty he never intended to inspire. Through his bumbling but well-meaning interference, he gradually reshapes the political landscape of Britain while struggling to manage his strained relationships with his cold half-brother Mordred, who secretly leads the revolutionary movement, his sharp-tongued childhood friend and fiancée Morgan, and the gentle maid Kei, who was the only person to show him kindness in his original doomed timeline.

The story follows Arthur as he travels to orphanages, negotiates with powerful saints, and confronts hostile noble factions, all while accumulating Good Deed Points and rewriting the record of his execution day by day. Each successful act of kindness shifts the future but also creates new complications, as his growing reputation as a saintly holy king attracts both devoted followers and dangerous enemies. The narrative balances lighthearted comedy derived from Arthur's panicked wheedling and the gap between his cowardly intentions and his heroic public image, with the underlying tension of a countdown toward the revolution he must prevent. The manga adapts the light novel series of the same name and follows Arthur's accidental transformation from a despised, sheltered prince into a ruler beloved by the very people who once condemned him.