Kokuou Heika, Watashi wo Katte Kudasai!: Imouto no Migawari de Mitsugimono ni Saremashitaga, Aisare inu wo Mezashimasu

Beatrice, who works as a maid in a brothel, is always compared to her beautiful younger sister, Elvira, and is always bullied by those around her. One day, she is offered as a tribute to King Gideon, rumored to be cruel and ruthless, in place of her sister. "Although I am a beast-man, I can only transform into a simple dog, not a beautiful bird like my sister ! If he finds out that I'm a substitute, I'll be killed, but my body has automatically transformed into a dog and I'm in dire straits ! But then I find out that Gideon is a dog lover and thinks I'm just an ordinary dog and is extremely fond of me ! I'm so happy I explode with joy, licking his face and feeling the height of happiness, but before I know it, I've turned back into a human... Which means that now I'm a woman who kisses His Majesty the King completely naked (death sentence confirmed)..." https://www.cmoa.jp/title/352768/