Ningen Fushin no Suterare Seijo wa Koisuru Kokoro wo Minai Furi

A "Resonance Mage" casts spells accompanied by melodies played on musical instruments. Among them, Müller, who excels in healing powers, was known as the Silver Sound Saint. However, she is framed and banished for using charm magic on the Crown Prince. Abandoned by her fiancé, she spends her days in despair until she meets Nacht, a soldier with a suspicious smile. She hopes he might hurt her. With that expectation, she spends a night with him, but since then he has been relentlessly pursuing her—!? A doting and obsessive love fantasy between a lonely saint and a quirky soldier!

(Source: Ichijinsha, translated)