Diana Is a Strange Mermaid is a Manga/Manhwa/Manhua in english language, ROMANCE series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

Once upon a time, in a certain country. A mermaid was brought to the castle. The strange mermaid with two legs was to be delivered to the king of a neighboring country... But when the prince saw her, he said, "You! Will you be my princess?!" And so begins an unexpected life together! How will the two (animals) love each other? A fairytale love comedy about two people who are in love, starting, starting...