The Kept Man of the Princess Knight Novel Volume 4 was written by Toru Shirogane and illustrated by Saki Mashima.

Upon returning to Gray Neighbor, Matthew and his companions are met with the unexpected scene of residents celebrating the Founding Festival. When they'd left, the city had been threatened by an impending stampede in the dungeon and the machinations of the sun god's preachers. The revelry makes it seem as though such concerns never existed at all. In this city full of corruption, citizens are usually indifferent to the plight of their fellow people. However, Arwin is willing to do whatever is necessary to resolve the situation… even if the plan isn't their best.