Ichiman Pound no Hanamuko

Clarissa is a daughter of an aristocrat, but after losing her parents at a young age, she spent a lonely childhood in boarding schools. And now, even her guardian uncle is gravely ill. If her uncle was to pass away, according to law she would lose all of her inheritance. To prevent this, she must marry, but her unpleasant, gold-digging cousin will not leave her alone. She decides to devise a plan and offers a proposition to a bankrupt 2nd son of an Earl; "Elope with me in return for my £10,000 inheritance!"

(Source: MU)