Rui has purple hair with a single streak of mint-colored highlights in his bangs and golden eyes. When he smiles, his mouth curves up like a cat's in a sly grin, and he often uses speech habits like "Oya" or "Fufu." His least favorite thing is vegetables. Once something piques his interest, his eyes sparkle, and there's no stopping his rampage. When he finds himself in a disadvantageous situation, he sometimes puts on a pitiful face and acts like a tragic male lead; his words and actions are always laced with sly charm and playfulness. Rui possesses exceptional talent, a brilliant mind, and a way of thinking that defies imagination. He is the Jellyfish Prince and has extensive knowledge about the surface world. Deep-sea creatures can freely maintain their human form (legs) as long as more than half of their bodies are not in contact with seawater. He seems to have spent most of his time on land researching life there. Through this, he happened to become close with Emu, who had also come to the surface, and he has developed feelings for her. He was troubled when his parents tried to arrange an engagement with the mermaid princess Nene. Since they only met when both were on land, he assumed Emu was a human and tried to give up on his feelings. He is 182cm tall! In human years, he is 19.

She has pale green hair and lavender eyes. She is a beautiful girl with fluffy hair, wearing her side hair tied low on both sides. She is an excellent singer and possesses a personality that is soft on the outside but strong on the inside. She is a bit of a reserved cynic who always says what needs to be said, and she's somewhat of a shut-in. Like Emu, she is a sea creature, but Nene is a Mermaid Princess. Recently, the Jellyfish Kingdom has been forcing an engagement between her and Rui. Nene finds it bothersome and hates the idea, so she occasionally goes to the surface to indulge in her hobby of gaming. She later realizes that the person Emu likes is Rui. Since she wouldn't have to go through with the engagement if Rui and Emu started dating, she is actively supporting Emu.