He’s Pregnant with the Major General’s Fish Cub

The little prince of the Empire suddenly became a mermaid. Since the fish’s tail appeared, he had been hiding it carefully.
Until he was hit in the head by a book, he foresaw an unknown (fake) plot—
In the book, he was gloomy and vicious. In order to obtain the throne, he didn’t hesitate to hook up with the youngest and most promising major general of the Empire and ruthlessly abandoned him after his success. Later, he was driven off the throne and locked up by the vengeful major general. He not only exposed his fishtail but also conceived the major general’s cub?!
Little prince: ??? He wouldn’t be with him even if he was cut into fish fillets!
Later, he really became pregnant with the major general’s cub..