"The Idaten Deities Know Only Peace" is an anime series set in a world where deities, known as Idaten, are created to protect humanity from demons. The story begins 800 years after the Idaten were first summoned by humans to end a devastating war against demons. These deities are immortal, tireless, and exist solely to maintain peace, but they lack human emotions and moral constraints. Over the centuries, the Idaten have eradicated the demon threat, leading to an era of prolonged peace. However, this peace is fragile, as humanity begins to forget the horrors of the past and the sacrifices made by the Idaten.

The narrative centers on a group of Idaten, including Rin, a stoic and powerful warrior; Hayato, a carefree and battle-hungry deity; and Ysley, a cunning and strategic leader. Their dynamic is tested when remnants of the demon race resurface, threatening the balance of the world. The demons, led by the enigmatic Zoble, seek to exploit humanity's complacency and the Idaten's emotional detachment to reignite chaos. As the Idaten confront this new threat, they are forced to grapple with their purpose and the ethical implications of their actions.

The story explores themes of immortality, morality, and the cyclical nature of conflict. The Idaten's lack of human emotions often leads to brutal and pragmatic decisions, raising questions about the cost of peace and the nature of justice. Meanwhile, human characters, such as the ambitious politician Paula and the idealistic soldier Miku, provide contrasting perspectives on the Idaten's role in society. Their interactions highlight the tension between humanity's reliance on the deities and their fear of their overwhelming power.

As the plot unfolds, the Idaten face internal and external challenges. Their unwavering commitment to peace is tested by the resurgence of demons, human betrayal, and their own evolving understanding of the world. The series balances intense action sequences with philosophical undertones, creating a narrative that is both engaging and thought-provoking. The Idaten's journey ultimately questions whether true peace can be achieved through absolute power and detachment, or if it requires a deeper connection to the humanity they are sworn to protect.