This Time, I Became a Fiancé of the Duke's Daughter, But Rumors Are Bad Personality, Ten Years Older.

Jared, the eldest son of a Baron family attending the Royal Academy, aims to become a Court Mage like his late mother. One day, after building up a track record through subjugation requests, his grandfather told him of his engagement to Olivier, the daughter of a Duke. Unaware that she is described as "the woman in this country most people don't want to marry," Jared visits the Duke's house and receives a harsh welcome from her. As a result, both express their desire not to marry, but those around them steadily prepare for the wedding. Jared's classmate Christa and childhood friend Jeni are worried about the situation. In fact, a sinister conspiracy was involved in that engagement...

https://www.cmoa.jp/title/338125/