Pipiko as known as "Pipi" was the first Tsundere in an anime show called "Triton of the Sea (Umi no Toriton) in 1972" was published by Osamu Tezuka.
She was found in Northern sea in a cool place. She wanted to become the queen of the Northen sea because she was the last mermaid
(Actually she still a badass Tsundere mermaid! xD ).
She's not very polite to a heroic young boy named "Triton". Triton saved her from a sea monster, but suddenly, she hated him. Why, is because after he strong saved them, all the other seal friends cheered him to become the part of the Northen sea. Proteus told Pipi that she was the Triton of all the sea and she has to stick with Triton, but she doesn't care about becoming a Triton although she hated Triton for obeying his order.
Pipi has a trick planned to get rid of him. She called Bach (His a friend of Pipi) and said that she will use an island illusion to trick Triton. She called Triton and together to find the island. Pipi's plan works tried to get rid of him.
Pipi was kidnapped by Minotus.
Triton said to her we have to get out of this place, but she wasn't listening to him. Proteus told them that they have to get out of this place before Minotus exterminate us. Pipi and Triton moved to an Island full of Dolphins and yep, she such a hater of Triton. She declaims to escape from him to go back her home. Triton shouted at her not to go back there and it's dangerous!
Next day, She missed her family and all of her seal friends. She hated sleep under the palm trees and sand. Triton said
"Is anything you wanted me to do?"
Pipi stubborn him for a while and show her anger expression. A second later, she answers,
"I felt uncomfortable to sleep here and THERE'S NOTHING TO DO IN THIS PLACE, IT'S TOO BORING!" she let a hmpt sound turning her head and ignore him.
Triton decides to make a house for her. He destroys all the palm trees with his deadly sword. Pipi screams and told him not to used his deadly weapons.
"IS THIS WHAT YOU WANT FROM ME, HUH!!!"
Triton used another way to get rid of the palm trees out. He calls all his dolphins to pull the palm trees out.
A few minutes later, Pipi was abused by Iru and Karu. Fin protecting her from them to stop abusing her. Pipi threw a rock at them unfortunately, she was punished by Triton!
She hated Triton and the other and manage to swim back to where she's belonging. Triton finds her although she's getting in deep trouble.
Once, He found her. She struggles with him and she told him she wanted to let go of him.
Triton against the sea monster and stabbed in the stomach.
Triton and Pipi now returned to the island where they finished building a house for her.
Next morning, Pipi call Triton and she wants to play a racing game. Triton was sick of her and said no thanks. She started to play rude thing to him.
Pipi: "Oh, because you're human, but you don't have a tail hahaha!"
Triton splashed on Pipi with an annoying anger expression.
She shouts back at him and said "BAKA!!!!"
Lucas the white dolphin came to her and asked that Triton has gone to help the human to defeat Doriate. Pipi was happy for him to leave (She hated him 93%).
On episode 10 "Come back Pipi",
Triton saw Pipi sitting on the rocky pool. She was annoyed him and pull out a raspberry at him. She was such a Tsundere to him and he disliked her. Pipi told all her information about her old friend from the Northern sea. Triton laughs at her with a grinning face. She then swims away from him not to talk to him anymore.
Pipi upset about him and along came a little yellow fish came by her. Pipi is only nice to the sea creature instead of a human. She helps the little fish to find her way back to her home.
They play tag and having fun together and unfortunately, they were almost trapped by the Poseidon's guards. The guards didn't know they were at. Pipi and the little fish hide from them and didn't make it for her home. They go back to the island where Pipi new home was. She thanks the little fish and suddenly, Triton shows off his angry expression. He shouted at her.
"WHERE HAVE YOU BEEN, PIPI!!!".
Pipi doesn't want to say about she's leaving the dolphins island and turned her head without looking at him.
Triton was even cross at her to waited for her answer. He walked up and shouted at her.
She told him she was trying to leave this place and go back where she belonging.
He smack her and yells at her not to go back their even he told her 10000000000 times!!!!
He asked her she has to stick with him and he even told her she's the Triton. Pipi don't want to be a stupity Triton.
She cries all day night in her hut. All of her fellows sang to her to cheer her up, but she still hated Triton. She wants him to leave this place.
Pipi found unusual huge pink shell ties from fin's back. Fin told her to be careful because this shell is belonging to Triton's family. She told her to listen to the sound effects of the shells. It was his family sounds. she thought for a moment. They told her the truth is she is the Triton. Pipi threw a shell toward far away from the island and she does not hesitate for that Triton.
After that, Triton came back from defeating Doriate. He told her she was a Triton. He told her that her family and mermaid groups were all dead by Poseidon and the Triton left was the onliest community who survived.
She told Triton a liar and having enough of that talks. Triton let her hesitate about what she had done from the beginning past.
Almost to the last episode of Umi no Triton, She is now better o know everything about Triton's rules.
Well, that all I've got to tell you about Pipiko. She is the first Tsundere anime mermaid in the anime series.
Here's the picture of her