Buried secrets come to light as we near the end of Part 4 of this biblio-fantasy! Rozemyne returns to Ehrenfest once more after her second term at the Royal Academy. Her days unfold peacefully as she meets her new little brother, searches for a younger retainer, tries her hand at cooking fish, and delves into her grandfather's past... yet she can't help but notice that Ferdinand is acting strangely.

The mention of Adalgisa deepens the mystery, and as Rozemyne ponders what it might mean, Ferdinand reveals a shocking truth to her. The secrets surrounding his birth, his final promise to his father, and a bitter choice... How will Ferdinand respond when the very future of Ehrenfest rests on his shoulders?

Find out in this volume, along with two new short stories and four-panel manga by You Shiina!