"Aterui" is an anime series set in ancient Japan during the Heian period, focusing on the historical figure Aterui, a leader of the Emishi people in the northeastern region of Tōhoku. The narrative centers on the resistance of the Emishi against the expanding Yamato state, which seeks to assimilate their lands and culture. Aterui emerges as a charismatic and strategic leader, uniting various Emishi clans to defend their autonomy and way of life against the encroaching forces.

The story begins with the Yamato court dispatching military campaigns to subjugate the Emishi, who are portrayed as skilled warriors deeply connected to their land and traditions. Aterui's leadership is tested as he navigates internal conflicts among the clans while devising tactics to counter the technologically superior Yamato forces. The series explores themes of cultural identity, resistance, and the cost of warfare, highlighting the Emishi's struggle to preserve their heritage in the face of overwhelming odds.

Key characters include Aterui, whose determination and tactical acumen drive the resistance; his loyal allies, such as the warrior Takamaru and the shamaness Yomihime, who provide both military and spiritual support; and the Yamato generals, who represent the imperial ambition and ideological clash with the Emishi. The narrative balances large-scale battles with intimate moments of character development, portraying the personal sacrifices and moral dilemmas faced by both sides.

The plot unfolds through a series of escalating conflicts, culminating in a decisive confrontation that determines the fate of the Emishi. The series does not shy away from depicting the brutality of war, nor does it romanticize the historical tensions between the Yamato and Emishi. Instead, it presents a nuanced portrayal of a pivotal moment in Japanese history, emphasizing the resilience of a people fighting for their survival and identity.