Yakai de "Tekitou ni" Hankachi wo Watashita dake Nanoni, Kishi-sama Kara Konyaku wo Semarareteimasu

Count Millietta, the daughter of an earl, is approaching marriageable age. At a fiancé-hunting evening party, she randomly hands a knight the handkerchief they first met... and the next day he shows up at her estate and proposes to her! Though confused, Millietta finds herself drawn to the kind knight. But the truth is... "I have no intention of letting you get away—no matter what it takes." Will his overprotective, overly loving nature (a yandere) gradually become clear? (Source: Kadokawa, translated)