Gokujou Kishi Danchou no Yuruginai Dokusen Ai
The Unwavering Possesive Love of the Stellar Knight Commander / 極上騎士団長の揺るぎない独占愛,

Cecilia, a lieutenant in the Arnault Night Watch, has loved its commander, Rudiger, since they were children. Now that they serve together, she keeps her feelings to herself while he energetically prods her in his role as her superior. When Cecilia hears rumors of women visiting “Asmodeus” to become beautiful, strange incidents begin occurring one after another. She investigates to protect the kingdom’s safety, but soon finds herself paired with an unexpected fellow investigator. Their inquiry unfolds alongside the feelings she has long kept hidden.