The Mermaid Prince's Revenge

Blurb If you could enter a story as the Little Mermaid, would you sacrifice everything for love? Everyone would say, "No way! That's so stupid!" Yumi thought so too. It was stupid. Why sacrifice himself just to benefit that scumbag man and that shameless woman?! If it were him, he could think of a hundred ways to change the ending! Then he transmigrated, straight into that famous fairy tale. He thought it was fantastic. He could rewrite the Little Mermaid's fate for sure! But once he figured out what was going on, he realized the story had already ended! The Little Mermaid had disappeared, and the beautiful hair of her five older sisters had been taken by the witch. Worse still, a grown man like him had turned into a mermaid! He was the Little Mermaid's younger brother, the little merman prince! They said he was the most beautiful jewel beneath the sea. Because he was so beautiful, the Sea King had kept him hidden deep inside the palace, afraid the wicked sea witches might covet him. Yumi was bewildered. What kind of ridiculous setup was this?! But speaking of beauty... In the original story, that scumbag had been attracted by the beauty of that ridiculous princess, hadn't he? Heh. Looks like the story could still go on after all. If he couldn't change the Little Mermaid's fate, then he'd just have to get revenge himself...