While strolling through Tokyo's bustling streets, Linn Suzuki stumbles upon a peculiar device protruding from the pavement. In a sudden twist of fate, she is ambushed by delinquents only to be rescued by a striking stranger who swiftly dispatches the assailants. Escaping the clutches of her oppressive mistress in Deep Kyoto, young Linn seeks refuge in Edo, yearning to reunite with her missing brother affiliated with the enigmatic Kuon Detective Agency. Serendipitously, the benevolent stranger reveals herself as Miho Kuon and offers Linn sanctuary, affectionately dubbing her Kotetsu, a nod to her sibling Tetsujin. However, as the shadowy Syndicate sets their sights on Miho, Linn finds herself entangled in a web of intrigue and danger.