Saeko Suuga holds a high-ranking command role in a multinational military coalition charged with safeguarding humanity from supernatural entities, such as demons and spectral forces. This autonomous organization supersedes the jurisdiction of individual nations, prioritizing global security. Stationed at Miyasaka High School in Japan—a nexus for demonic incursions due to an unstable dimensional portal—she oversees the training of student council president Gekkou Kurenai, the sole individual capable of activating the gateway, and Taito Kurogane, a newly inducted council member manipulated by Gekkou’s influence. Her mission centers on preparing them to manage supernatural threats.

Rigorously disciplined and meticulously organized, Saeko excels in tactical data analysis and mission coordination, proving indispensable in her military operations. Conversely, her domestic aptitude falters; culinary endeavors frequently spiral into chaotic mishaps. She shares a closely aligned professional rapport with Yuuichi Philier Cross, her interactions subtly hinting at deeper, unspoken sentiments.