Juuboku to Torikago no Hanayome

Fujino, now 18, belongs to an age-old family of prestige. She's been sheltered her entire life, having been raised under her family's strict rules. The only person who truly shows her kindness is Hiro'omi, her father's personal attendant. Unfortunately, that compassion has caused her to fall head over heels for him! A tale of a meek and pure-hearted heiress, and her forbidden affections for her family's servant. (Source: MangaPlaza)