Poseidon's Chosen Queen

Serena, an orange-tailed mermaid disguised as golden royalty, is betrayed and killed by her fake saint husband. Reborn, she is sacrificed to the Abyss, where she meets the hidden Sea God. They fall in love and bear the divine Chosen One. Serena exposes the villain, avenges her past, abolishes the cruel scale caste system, and becomes the rightful Queen of the Seven Seas.