Rien wa Itashikanemasu!

In the Taisho era, Chiharu was the eldest daughter of a well-off landowner's family, but she had a "secret." It was a large birthmark covering her back, which caused her to be rejected numerous times for marriage, until the spring of her 28th year. Then, her father took her to a party, where she met a man named Seta. When she asked about the handsome stranger, she was told that he was a womanizer who made his fortune in "unsavory businesses." However, it was Seta who asked Chiharu to marry him, in exchange for covering her father's debts for his failed business. So begins the clumsy contract marriage between the two in a Taisho-era romance story!

(Source: Mecha Comic, translated)