The man I had a one-night stand with turned out to be my fiancéThe Man I Spent One Night With Turned Out to Be My Fiance; One Night Stand Otoko wa Kekkon Aite de Shita; The Man I Spent One Night With Turned out to Be My Fiancé; ワンナイトした男は結婚相手でした

Luce, the daughter of a duke, falls into despair after her stepsister steals her fiance. As a replacement, she is arranged to marry Arnolfo, a man feared by all and known as the "Marquis of Death." Before facing this unwanted marriage, Luce decides to make one last memory as a single woman by attending a masquerade ball where she ends up spending a night with a mysterious man. She intends to keep that night as a secret tucked away in her heart until she meets her husband for the first time on their wedding day only to discover that he is the very same man from that one-night encounter! Luce doesn't want him to think she's a shameless woman who plays around at night, so she decides not to reveal her identity. However, Arnolfo sweetly desires her every night, and she finds herself giving in again just like that night! [Original Webtoon](https://www.comico.jp/comic/11878)