Seira

Seira's brown hair is gathered into a ponytail, and her tail is pink with purple markings along it. For accessories she wears headphones fashioned from shells, a yellow bikini held by blue floral straps, a necklace strung with red pearls, and red lipstick.

As mermaids tend to be, Seira is gentle, warm-hearted, and clearly fond of having fun. When she first crossed paths with Luffy, Usopp, Sanji, and Chopper, she praised how daring they were to slip onto Fish-Man Island without permission and declared her love of pirates, which likely explains why she takes to Sanji the way her friends do.

Her race grants her the usual mermaid gifts: she can breathe underwater, swim at speeds well beyond the flying fish ridden by the Flying Fish Riders, and possibly call to fish with sonar, though she is left helpless once on land. She is also a talented dancer. Seira and her companions first turned up at Mermaid Cove, greeting the Straw Hat Pirates after Camie brought the crew over. When the three princes came asking about the crew's unlawful arrival, the mermaids concealed the pirates, but Sanji's nosebleed and Hammond's attack gave them away, after which the princes explained they merely wished to pass along Jinbe's message to Luffy. Once the conflict with the New Fish-Man Pirates was settled, Seira and her friends performed at the Ryugu Palace banquet held for the crew and bid them farewell as they set out for the New World. Some while later, she and her friends watched Caribou attempt to abduct a defenseless mermaid.