Once a year, the sovereign witches of Egregore Seven gather for a tea party. This year's event is hosted in Sapporo, Japan, and the task of security falls to Section Eight, a new, experimental division beneath the National Public Safety Commission tasked with preventing magical crimes.

Captain Reiko Nakamura is the only veteran among a squad of academy graduates. But when an Egregore is assassinated by an unknown assailant, the team, and the rest of the city, are caught in an unpredictable web of spells and statecraft, while Reiko's buried history threatens to endanger the lives of everyone around her.