Kei Asagiri, a boy with a fragment of his soul in the Netherworld, wields potent black flames at the cost of his dwindling soul. Employed as an 'Antique Hunter,' he encounters a peculiar group who transports him to the outskirts of Koarun Academy City. Unexpectedly, he becomes the custodian of a rare antique: a blonde girl named Victoria. She serves as the key to safeguarding Kei's soul from being consumed, requiring daily kisses to exchange magic power. This peculiar pact offers Kei liberation from his soul's peril and sustains Victoria's human guise, fostering an unconventional alliance between them.