I Became the Black Swan Mother of the White Swan Princess

The possession that happens to others befell on me too. I’m pretty sure that I’m a supporting character… But what on earth is this novel? On top of being a widow with stepdaughters of my age, I’m living a cursed life in which I transform into a black swan every night because of black magic! I need to suppress my tears and change my fate… Not. Why should I? Why so serious? A duchess by daytime, and a carefree queen of the lake by nighttime. Bravo, my destiny! Life should be spontaneous! As much as I wished to continue living like this, I chanced upon a white baby swan. “Mommy, awe you weally my mommy?” What, you’re a human? And the tyrant emperor’s youngest sister moreover? “I’m not your mommy! Can’t you tell from the colour of our feathers?” I’m a black swan, you’re a white swan! But why’s she so freaking adorable?! As we endure the obsession and persecution(?) of her seven older brothers, including the tyrant emperor, can our mother-daughter love ever be fulfilled? (Source: KakaoPage, translated)