After becoming a teacher at Kusunoki Girls Academy, Kaoru had fallen in love with a colleague and was moving toward marriage. But suddenly, an unexpected summons shattered his life. From Yumiko of the Yabuta Group came shocking news—his older sister Miwako was living as a slave. Soon after, Kaoru himself would be kidnapped and subjected to the same fate as his sister. To uncover his family's whereabouts and fight for his own survival, he begins a new battle.