MARs decides to enjoy their day at the beach after being sent there on work-related business, but once again they run into their long-time rivals, Serena and Kanon. As it turns out they must compete against each other to locate a dolphin with a heart shaped mark on it called the legendary Venus dolphin.
Excitedly MARs finish their program shoot. The staff compliments their work and wish them luck with the rest of their work for the day. Aira is bursting with excitement, but Mion reminds them of the work they need to concentrate on, with Rizumu disappointed they will only be there for about two days. Kyoko tells them to stop complaining an focus on their work and Mion asks Jun to help Aira calm down a little. As it turns out, none of the adults are helpful, and Rizumu brings up they don't have their schedule. Mion can't help but worry when Kyoko remains vague.
Suddenly the girls spot Kanon and Serena on a small, hand-built stage nearby. They announce their plans to take their comedy one step further while working as Prism Stars. Right away Mion can tell this was a part of Kyoko's plans and all five girls express disbelief after they are told of the Survival Challange they will take part in as they sail across the waters. The staff explains that they must locate the special dolphin with a heart-shaped marking on its head, basically a treasure hunt. They ask what makes it special, or even a Survival Challange and they explain that the girls must live off of the land until one of them finds this specific dolphin. Then they will perform with it in a large Prism Show together.
They arrive at the island, and the cameraman explains that the girls will be filmed from time-to-time, but for the most part, they will probably be alone. They try to negotiate with the men, who are still on the boat but they take off as the girls panic at the prospect of a giant shark being in the water surrounding the island. They quickly take off and Aira suggests they work together- but this is instantly rejected by Serena, Kanon, and Mion.
They split up, with Mion reminding Aira the dolphin wouldn't be so special if it was easy to spot. She suggests they just concentrate on surviving and they see Rizumu trying to start a fire with a large piece of meat. She reveals its easy to adapt because of SurvGirls, a book about love and surviving it; with some helpful survival tips. Suddenly they see splashes in the water, so Mion and Rizumu dive into the water for a closer look. There they find a baby dolphin stuck in netting and free it, taking a moment to fill Aira in on what happened after she uses a floaty to approach them on the surface. The dolphin has been there for a while and its still weak, so they dive back in to check on it and bring it back to the surface as Aira expresses relief.
At the dock, the girls check on the dolphin while Aira explains she misunderstood them and thought they ran into a shark. Rizumu names the dolphin Kuchibashi and Mion managed to identify him as a longnose dolphin. She finds it strange he's by himself and they realize he must have been separated from his family. Rizumu suggests they try to find his parents, refusing to leave Kuchibachi alone like this. Both girls understand and agree to lend a hand, deciding not to care about the filming that may or may not be going on. The girls search around the island but are unable to find anything other than seas of fish while Rizumu bonds with Kuchibashi.
As this is going on, Kanon and Serena try to fish for the dolphin. As it turns out they only managed to catch Penguin-sensei. He dives back into the water and they snag something else, this time Yamada- effectively scaring them as he surfs away with Penguin-sensei. The director shows up to speak with the girls and asks if they found the dolphin yet, pointing out that MARs has.
The trio resume searching, with Rizumu refusing to give up. Suddenly the girls spot a shark up ahead and quickly try to swim away until seeing Kuchibashi stuck behind. Rizumu grabs the oar and quickly beats it up, but Mion thinks something is wrong. To their shock, they find Serena but don't realize she was in the Shark, a costume.
The director decides the girls will still go on to perform, starting with Kanon and Serena. They perform two Prism Jumps, the Hat Trick Star and Prism Rainbow Hurricane, then end their turn. As the girls watch, Kyoko reveals herself-entirely burnt-along with Jun's face. MARs prepares for their performance, but Rizumu is unhappy, seeing how alone Kuchibachi is. Jun gives her some advice but must be translated by Mion before Rizumu realizes that if she performs well enough, Kuchibashi will remember her and that he isn't alone. They think it would cheer him up and Rizumu promises to work hard for his sake. They grab their Batopon and start their performance, with Aira and Rizumu performing Heartful Splash Duet, along with Kuchibashi, surprising them. When they see that he wishes to dance with Rizumu, she goes on to perform a new Prism Jump, Dolphin Venus. To their surprise, two other dolphins appear, followed by several more to complete the jump with her.
They end the performance, spotting a herd of heart dolphins and Kuchibashi swims off to join them. They see his parents there and happily congratulate him as they realize they also won the survival challenge. Rizumu says goodbye as Kuchibashi swims away with the other dolphins.
That evening, back at the office the group watch the filming that took place. They admire everything that went on, but Aira believes something may be missing. As it turns out, Serena and Kanon were entirely cut out of the filming- causing Serena to angrily lament the turn of events.
Prism Stone Shop Segment
Akkina starts the segment by reminding the girls they are now Platinum trainees. She congratulates them, then asks how their training has been lately. They explain they enjoy it- but it was a lot of hard work. Akkina shows the girls the screen and decides they must learn now how to sing. They are sure they will be fine, and she informs them they will be one step closer to their debut, although the singing practice will be very hard. A famous teacher will be helping them, and decides they will practice "You May Dream". The girls decide to start practicing right now and show a video of it.
Rabi-chi, Bea-chi, and Neko-chi explain that the girls will be learning to sing with Me-Me-Sensei, a famous teacher. They formally meet her and show her their progress so far. The Mascot teachers note that Me-Me seems thoughtful while watching them, complimenting their mood but pointing out they sang off key a few times. This worries the mascots and they tell the audience to keep watching to see how they perform next time.
Characters in Order of Appearance
- Film assistant