"Endro~!" is a fantasy-comedy anime set in a world where heroes and demons coexist. The story revolves around a group of four young adventurers—Yūsha, Seira, Fai, and Mei—who are tasked with defeating the Demon Lord to bring peace to their land. Yūsha, the self-proclaimed hero, is determined and optimistic but often clumsy and naive. Seira, a skilled swordswoman, is serious and disciplined, contrasting with Fai, a laid-back and mischievous mage. Mei, the youngest, is a shy and kind-hearted cleric who often struggles with self-confidence.

The group embarks on their journey, guided by their mentor, Rona, a cheerful and eccentric priestess. However, their quest takes an unexpected turn when they accidentally send the Demon Lord back in time to her childhood during a confrontation. This twist results in the Demon Lord, now a young girl named Mao, enrolling in the same adventurer school as the heroes. Unaware of Mao's true identity, the group forms a bond with her, leading to humorous and heartwarming situations as they navigate their training and daily lives.

The narrative blends traditional fantasy tropes with slice-of-life elements, focusing on the characters' growth, friendships, and comedic misadventures. The dynamic between the heroes and Mao creates a unique tension, as the audience knows her true identity while the protagonists remain oblivious. The series balances lighthearted humor with moments of character development, exploring themes of camaraderie, self-discovery, and the blurred lines between good and evil. The episodic structure allows for a mix of standalone adventures and overarching plot progression, culminating in a resolution that ties together the characters' journeys and their evolving relationships.