"Yūsha Party o Tsuihō Sareta Shiro Madōshi" centers on a white mage named Whit, who is expelled from his hero party after being deemed useless in combat. The party, led by the warrior Cain, includes the archer Aria and the black mage Lydia. Despite Whit's crucial role in healing and supporting the group, they dismiss him, believing his abilities are unnecessary for their quest to defeat the Demon Lord. Whit, disillusioned and betrayed, decides to forge his own path, leveraging his extensive knowledge of magic and combat strategy.

After his expulsion, Whit encounters a cursed sword that grants him immense power but at a cost: it drains his life force. Determined to prove his worth, he embarks on a journey to master this weapon and refine his skills. Along the way, he forms new alliances, including with a skilled swordswoman named Maria and a mysterious alchemist named Rina. Together, they uncover deeper conspiracies surrounding the Demon Lord and the true nature of the hero party's mission.

As Whit grows stronger, his former party begins to realize the gravity of their mistake. Cain and the others struggle without Whit's support, facing increasingly dangerous foes. The narrative explores themes of betrayal, redemption, and the redefinition of strength, as Whit challenges the conventional roles of healers and mages in a world dominated by physical combat. The story builds toward a climactic confrontation where Whit must confront both his former allies and the Demon Lord, redefining his identity and purpose in the process.