Ringoku ni Koshi Ire Shita Oujo Tsuki Mofumofu Jijo desu ga, Hontou no Oujo wa Watashi nandesu: Tachiba to Koe wo Ubawaremashita ga, Inochi no Kiki ni Sarasarete Iru node Boukan Shimasu

Elvir is a princess born to the king of the volcanic nation of Fastu and her wildcat-beast mother. Although she was born out of wedlock, she was given the status of princess as an exception, and was to marry Arnold II, the king of the great nation of Zugvogel. However, he was known as the "cursed king." What's more, her half-sister, Ruby, who had always harassed her, was to accompany her to the wedding as a maid!

(Source: Kodansha, translated)