Konyaku Haki sareta "Kuuki" na Watashi, Nariagari no Dannasama ni Totsugimashita.

Iris, the daughter of a marquess, not only had her fiancé stolen by her younger sister, but she also ended up having to marry Lord Lucas, a nouveau riche merchant who was shouldering her family's debts. However, this former-commoner-turned-baron's reason for marrying her was just to have Iris teach him and his servants how to survive in high society!

"I was told that I lack presence and that I'm like air. If someone as plain and dull as myself could be of any use to you, I will be more than happy to help, Lord Lucas," Iris said with complete seriousness, throwing Lucas off guard. Will Lucas be able to resist being slowly drawn to the dedicated Iris, who strives to support him and the people in her life? A complicated romcom that starts with a marriage blanc begins here!

(Source: Cross Infinite World)