The story begins with Abel Castor, a 33-year-old former legendary hero known as the "Great Sage" and "Great Archmage," being expelled from his adventuring party by its leader, the 18-year-old hero, Jerk Mond. Jerk, who wields the sacred sword and possesses the unique "Hero" job, believes Abel, whose white hair and failing body suggest old age and a decline in magical power, is no longer worthy of being on the front lines. Abel, despite his physical deterioration, wishes to stay, revealing his deep affection for Jerk and his companion, Tear Serage, a saint with healing abilities. Abel had found them as orphans ten years prior, after defeating the Demon God, and raised them like family, teaching them the ways of adventuring. He admits he has been relying on Tear's healing magic to cope with his mysterious ailment, which doctors and curse specialists cannot diagnose. Jerk cruelly reveals that Tear has been complaining about the burden of healing Abel every night, claiming she no longer wants to do it. This revelation deeply wounds Abel, who realizes his presence is a strain on Tear. Jerk further states that he has already recruited a skilled elf to replace Abel and that he and Tear no longer need him. Heartbroken and feeling rejected by the closest thing he had to family, Abel agrees to leave, gifting his valuable equipment to Jerk. He attempts to give back a ring, a cherished memento from Jerk and Tear, but Jerk callously rejects it, claiming Tear doesn't even want to see Abel. As Abel departs, he sees Tear leaning on Jerk, leading him to the painful realization that they are lovers and his perceived family was a one-sided affection.
Abel retreats to the remote northern frontier town of Myokou, seeking solitude. He lives a meager existence, foraging for herbs to sell, and avoids all contact with the townsfolk. Six months pass in this isolated state until a local apothecary, Mateo, approaches him with a plea: a child has gone missing in the nearby forest. Despite his desire to remain uninvolved, Abel is moved by the situation and agrees to search alone, as his weakened state cannot protect a group. Using his innate magical senses and a stealth spell, Abel locates the child, a young girl named Rinrin, who is trying to save a small, injured dragon. Abel recognizes the dragon's ailment as a curse and, despite his depleted internal magic, uses his life force to cast a powerful dispelling magic. This act not only heals the dragon but also inexplicably restores Abel's own strength and magic, transforming the dragon into a beautiful woman. She reveals herself to be a Divine Radiant Dragon, a powerful beast, and thanks Abel, forming a contract with him.
Meanwhile, Jerk gloats about his successful plan: he had cursed Abel with a weakening spell via the ring he gifted him, draining Abel's power to fuel his own. Jerk's motives were jealousy of Abel's power and affection for Tear, who he believes loves Abel. He manipulated Tear into believing Abel left due to his worsening condition. However, Jerk is unaware that the dragon's scales reflected Abel's dispelling magic back onto him, breaking the curse and transferring Jerk's stolen power, including his own Hero abilities, back to Abel. Jerk is left weakened and his own powers are draining away.
Back in Myokou, Mateo, who had previously seen Abel in the capital and recognized him as the Great Archmage, apologizes profusely for putting him in danger. She offers him her entire fortune and her apothecary business as compensation, intending to sell herself into slavery to make up the difference. Abel refuses, stating he acted on his own will and that he is no longer the legendary Archmage but simply "Bell." Mateo, touched by his refusal and his kindness towards her niece Rinrin, confesses her love for him.
Their conversation is interrupted by Monba, a gatekeeper, who brings in a severely poisoned female adventurer, Hitomi Ran. Mateo identifies the poison as Hydra venom, but without knowing the specific creature, she cannot create an antidote. Suddenly, Abel sees a translucent window displaying Hitomi's status, revealing the Hydra's poison. Mateo recognizes this as the rare "Appraisal" skill, typically exclusive to Heroes. Abel, surprised to possess this skill, uses it on himself and discovers his job has changed from "Great Sage" to "Great Hero (SSS)" and his health is fully restored. He realizes his encounter with the dragon and the subsequent events have caused him to evolve.
Later, Jerk, consumed by jealousy and overconfidence, experiences severe physical symptoms, including vomiting blood, a sign that the curse is backfiring. He ignores these warnings, believing his newfound power will secure Tear's affection.
Abel, now fully restored and possessing the Great Hero job, learns that Hitomi, an S-rank adventurer, was poisoned while fighting a Hydra. He uses his restored magic to heal her and, with the help of the Divine Radiant Dragon, Pure White Dragon, whom he has inadvertently taken responsibility for, he defeats the Hydra with overwhelming power. The townspeople, who have come to know him as "Bell," hail him as a hero for saving them from the Hydra, unaware of his true identity as the legendary Archmage Abel Castor. Hitomi, recognizing him from his past deeds, asks him to be her companion to become stronger and save others, but Abel, still scarred by his past rejection, refuses. However, Hitomi then asks to become his disciple, and with Mateo's encouragement, Abel reluctantly agrees. He is now a hero in Myokou, his desire for solitude thwarted by the unfolding events and the people who have come to rely on him.
