Reborn: I Gave My Sister the Merman and Took the Octopus Incubus

Nina was killed in her past life by her sister Ivy using the octopus demon Cassian's poison — while her merman mate Elias watched coldly from outside the door. Reborn on the day of choosing a beastman, Nina discovers Ivy has also returned. Ivy lunges at Elias first, threatening suicide to swap mates. Her adoptive parents favor their real daughter. Elias chooses Ivy and humiliates Nina as a "lowly foster child."

Heartbroken, Nina willingly picks the feared octopus demon Cassian — dangerous, lustful in reputation, but gentle and obedient to her alone. Because in her past life, Nina once saved his life. Ivy gets Elias but finds only misery, repeating her former suffering. Nina seals a true mate bond with Cassian — the man the whole world fears, but who stops for no one but her.