"Ecchan no Sensō" is a historical drama set in the tumultuous period of Japan's Sengoku era, focusing on the life of a young woman named Echizen, who becomes entangled in the political and military conflicts of the time. The narrative begins in a small village where Echizen, a skilled herbalist, lives a peaceful life with her family. Her knowledge of medicinal plants and healing techniques earns her respect within her community. However, her life takes a drastic turn when her village is raided by a rival warlord, resulting in the death of her family and the destruction of her home.

Driven by grief and a desire for justice, Echizen disguises herself as a man and joins the ranks of a powerful daimyo, Oda Nobunaga, who is known for his ambition to unify Japan. Under the alias "Echigo," she quickly rises through the ranks due to her strategic mind, combat skills, and deep understanding of the land. Her dual identity becomes a central tension, as she must navigate the rigid gender norms of the era while maintaining her cover. Along the way, Echizen forms alliances with key historical figures, including Toyotomi Hideyoshi and Tokugawa Ieyasu, who play pivotal roles in shaping Japan's future.

The series delves into the complexities of war, loyalty, and identity, as Echizen grapples with her personal vendetta and the broader implications of her actions. Her journey is marked by battles, political intrigue, and moments of introspection, as she questions the cost of vengeance and the possibility of reconciliation. The narrative also explores the relationships she builds with fellow soldiers, some of whom begin to suspect her true identity, adding layers of tension and drama.

As the war progresses, Echizen's role becomes increasingly significant, influencing key events that lead to the eventual unification of Japan. The series concludes with her confronting the warlord responsible for her family's death, culminating in a climactic battle that tests her resolve and principles. Through its portrayal of Echizen's transformation from a grieving villager to a key player in Japan's history, "Ecchan no Sensō" offers a compelling exploration of resilience, sacrifice, and the human cost of war.