My Happy Marriage (Light Novel), Vol. 6

Kiyoka has been imprisoned, and Miyo takes it upon herself to rescue him by whatever means necessary. But when she arrives at military HQ, she comes face to face with a stunning young man...who looks exactly like Kiyoka. Claiming to be Kiyoka's familiar, he takes Miyo back to the Usuba household where she decides to turn over a new leaf-by carving her own path to reuniting with Kiyoka.