Firefly Wedding - Hotaru no Yomeiri

Satoko Kirigaya has everything a noblewoman could want—except time. With her life running out, she’s determined to marry well and make her father proud. But when a ruthless assassin kidnaps her, she makes a desperate offer: “Marry me, and we’ll have it all.” Shinpei Goto accepts, only to become dangerously obsessed. Now Satoko must choose between duty and a love that could consume them both.