Mommy Is the True Sea Queen

A thousand years ago, the Kingdom of Alester killed the Abyssal Sea Monster's child, forcing every king to sacrifice a princess. To save her mother, illegitimate daughter Marina is drugged by her half-sister Serena and forced to marry in her place—but Poseidon, the Sea God, rescues her, and they spend a night together. Nine months later, Marina gives birth to sextuplets with divine powers and raises them alone; six years on, she meets Poseidon again.