Hana to Yumehiko

It's the Taisho era, and Tougane Hana has become the daughter of a nouveau riche family thanks to her father's huge business success. However, she struggles to fit in at the aristocratic school she attends. Then, her father brings in Kitaoji Yumehiko, the son of a fallen aristocrat, to teach her manners...

(Source: Hakusensha, translated)