Sultan no Koukeigi

A man named Najib unexpectedly arrives at Rosalind's home with startling information: her deceased husband was heir to the throne of the vanished kingdom of Bagestan, making her son the rightful successor. Najib, claiming to be Jamshid's cousin, was searching for the al Jawadi Rose, an heirloom only the true descendant can hold. To safeguard the boy from those wanting the throne, he proposes a fake marriage with Rosalind.