Once a year, the sovereign witches of the 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.

Section Chief Kazuo Shinomiya and Captain Reiko Nakamura are the only veterans 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 Kazuo and Reiko's buried histories threaten to endanger the lives of everyone around them.