Haruka, Makoto, Rin and Nagisa are all cute little boy swimmers of the Iwatobi Swim Club. One time, they had a field trip to a huge sports complex and got to swim in one of the pools to relax after practicing.
“Does anyone feel something…weird about this pool?” Makoto said.
“What do you mean, Mako-chan?” Nagisa asked. “The water’s fine…look at Haru-chan, he seems to be relaxed on the water.”
“Well that’s because Haru’s kind of…obsessed with water…” Makoto replied.
“Must be your imagination, Makoto. Nothin’s wrong on my side of the pool, heh.” Rin said while looking at the sun.
Meanwhile, another swimmer joined in.
“I-I just arrived here…” the boy with glasses waved at them. “I’m just training to be a swimmer…”
“Ohh…” Nagisa went towards him and took his hand. “Then we’ll be glad to teach you!”
“W-wait! H-hold on a sec!” the boy said as he took off his glasses and put them on the side of the pool.
“It’s gonna be fun!”
“Nagisa, you’re hurting him!”
“Oh…sorry.” Nagisa lets his hand go and the boy slips, but was rescued by Haru.
“Are you okay?” Haru asked.
“What’s your name?” Nagisa asked.
“Then I’ll call you Rei-chan!”
“R-rei chan!?” Rei was surprised and embarrassed.
Anyways, the five boys enjoyed swimming under the sun. But suddenly, Makoto felt that strange feeling again.
“Guys…I really feel weird this time…like I’m having a fever…”
“Come to think of it, I do feel it too…” Nagisa said. “How about you Haru-chan? Rin-chan? Rei-chan?”
“I feel as if my clothes becoming smaller.” Haru said.
“Ughh…me too, I feel like we’re in a steam bath…” said Rin.
“The temperature does seem a bit off from what should be of standard pools…” said Rei.
“I really wonder what’s going o—”
Nagisa suddenly covered his mouth.
“What is it Nagis—oh my God!” Makoto also covered his mouth, shocked to hear a change in his voice and Nagisa’s.
“W-what’s going on here?!” Nagisa started to cry and hug Makoto. “What’s happening to us?”
“Haru…your face…” Rin was shocked.
“You too, Rin…” Haru replied. “Your body as well…”
“And Rei-chan too!” Nagisa exclaimed.
“Is this pool…” Rei thought deeply with anxiety. “…aging us rapidly?”
“Huh?” Makoto looked at his arms. “Y-you’re right…my arms look different now…”
“My body is starting to look different too…” said Nagisa. “Not to mention all of our voices are starting to change…”
“We’d better get out of here, quick!” Makoto told the group.
As they quickly got off the water, each of them was amazed to see the changes that had happened to their bodies. Makoto and Rin suddenly gained muscular bodies, Rei and Haru grew a lot as well, and Nagisa too, except his voice wasn’t as low as the others’.
“Not bad…” Rin smiled. “I like this body; don’t you think so, Haru?”
Haru nodded. “Rin…your teeth…”
“Huh?” Rin put his fingers to his mouth and felt really sharp teeth, like a shark’s. Then, he smiled.
“Woah…!” Nagisa was amazed. “Even Rin-chan’s teeth changed…he really does look like a shark now! A-and look at Mako-chan’s body…he really does resemble an orca now! Tee hee!”
“Hey, cut it out, Nagisa…!” Makoto was embarrassed.
Suddenly, Coach Sasabe went by and was shocked.
“W-who are you guys?”
Then, he looked closer at them, as Rei picked up his glasses from near the pool. The coach then glanced at the pool.
“This is…the legendary mysterious pool…and if Haru and the others said that they’d be around here than that must mean…”
“We’re so sorry, coach!” Makoto scratched his head and smiled.
“Yeah, we didn’t know that the pool had magical powers like that!” Nagisa pouted.
“Even this new kid,” Rin said as he points at Rei, “grew up with us.”
“Hmm…” Coach Sasabe thought. “I think that it’s best you go to the other pools instead. Got that? We’ll try to work out something with what’s happened to you. The mysterious pool might age you further or do something horrible!”
With that, the coach left again and the five swimmers went to another pool that was much wider than the mysterious pool.
“I don’t feel anything strange here anymore…” Makoto sighed. “Thank goodness.”
“Alrighty! Let’s just enjoy our day off!” Nagisa cheered.
While the rest of the gang was busy, Haru was floating in the pool alone, with his newfound body.
“This body…even though it’s big, it’s very light…”
“I think I’ll doze off a bit…” he smiled as he stared at the sun.
Haru fell asleep for a while in the water, but when he woke up…
“W-where is everybody?”
He suddenly noticed that his arms seem to be missing or have taken a different form. His legs had become fins.
Haru turned around to see an orca, a penguin, a shark and a butterfly.
He then realized that he turned into a dolphin.
Haru was sweating as he jumped out from his bed, realizing that it was all just a dream.
Meanwhile, during the joint practice of Iwatobi and Samezuka, he heard Nagisa talking about a strange dream with Rei and Makoto.
“…and then, after our bodies aged and gained muscles, we went to other pool and became aquatic animals! Except for Rei-chan who became a butterfly.”
“H-hey!” Rei shouted.
“But still, it was really weird!” Nagisa told them.
“I had the same dream, too!” Haru interrupted.
“Looks like all of us had the same exact dream, huh?” Makoto smiled.
Rin suddenly passed by.
“Hm? What’re you guys talkin’ bout?”
“Rin-chan, I mean Rinrin!” Nagisa approached him happily. “We were just talking about this weird transformation dream that all of us had…” and then Nagisa told him about it.
“So, did you have the same dream?”
“Well I…” Rin smiled and looked at everyone, and then he laughed.
“Best dream I ever had.”
“Rinrin!” Nagisa hugged him. “Heheh, I knew you would!”
“C-cut it out, Nagisa!” Rin shouted.
“Hey, Nagisa, let go of him!” Makoto said.
Meanwhile after the practice, Captain Mikoshiba called out Nitori to accompany him to a certain place – a large sports complex with two pools.
“Nitori, listen.” Mikoshiba told him as he undressed and stood near the larger pool. “My time as the captain of Samezuka Academy is over. I’ve passed the title to Rin, because he deserves more. As for me, well, I’m going back to my old time period.”
“T-time period?” Nitori asked. “W-what are you talking about? And why are you leaving us all of a sudde—”
Mikoshiba hugged Nitori and smiled.
“I don’t guarantee that I could return back from the future time that I was originally in, but I’m sure we can all meet again.”
“Captain…!” Nitori was crying.
“My final advice: go into that other pool and live anew! Good luck on your journey!” Mikoshiba then jumped into the pool and opened a vortex that warped him to another time era.”
Nitori then jumped into the other pool, crying in tears and trying to drown himself. But after a few minutes, he got off the pool and noticed a significant change in his body and his voice.
Probably because of the effects of the pool, Nitori’s eyes became blurred as well, and when he was going outside, he rode on a different bus by accident. He was then hit by a speeding car which made him lose all of his memories of the swimming teams and started a new life as a student in Himalaya Third Technical School, named Koichi Mochizuki, and started wearing glasses.
Meanwhile in the future, Mikoshiba went back to his old identity as one of the “seven kings”, Mikoto Suoh, who controls fire.