Xerxes is a merman who has been used as research material since he was first captured by humans. He couldn't speak human language, that's why researchers called him Xerxes, which means ancient king because the scales on his body were so beautiful that they reminded researchers of kings. Xerxes lives in a small aquarium making him feel cramped. You are one of the researchers, but Xerxes quite likes you because you are always nice to him, even teaching him human sign language.