Yuusaku has an idea, ``Let's rent boats and race to that offshore island.'' Kyousuke thinks this is just like Yuusaku, so into fitness. They split up with Kyousuke and Madoka in one boat while Yuusaku and Hikaru share the other (Hikaru lost the lottery). Madoka offers to row for a while, but Kyousuke turns her down and continues, not wanting to look weak in front of Yuusaku. The current separates the two boats, and eventually they lose sight of each other. Kyousuke finally decides to use his power to help, and gets the two of them to the island that way. Madoka is impressed by his last spurt of rowing, but he's already asleep from fatigue.
Kyousuke's father and sisters are on the ferry boat to this resort. Komatsu is taking pictures of the gals, and Hatta is helping. The gals remember back to when they were leaving home. They comment that Kyousuke will be surprised by their showing up. Kurumi wonders if he's in the middle of doing ``something bad,'' scandalizing Manami. They walk out the door to find Komatsu and Hatta ready to join them. The two wonder how these fellows managed to hear about this, ``Maybe their ears have `power'.''
Kyousuke wakes up to find that Madoka has wandered off. He goes to search for her and finds a hidden pool where a mermaid is bathing. ``That moment, I met the fairy of this tropical island.'' She looks a lot like Madoka. He dives in after her, and when he runs out of air, she touches his nose, fixing that problem for him. However, it was a daydream. Kyousuke snaps out of it when Madoka yells at him for watching her bathing.
Later they talk about this being an uninhabited island, and wonder if Hikaru is ok. Kyousuke replies she should be, ``He's with her'' and does his Yuusaku imitation. Madoka laughs at this and threatens to tell Yuusaku. Kyousuke thinks that this place is a paradise. He compares it to ``that movie'' (Blue Lagoon), but thinks that the two in that movie went too far. He and Madoka then have great fun playing on the beach.
Hikaru is trying to cheer Yuusaku on to get to the island, but he's simply too tired. They end up going in a big circle and arrive back at the beach they left from just as the ferry boat with the others passes by. Hikaru greets them so enthusiastically that she tips over the rowboat.
Back on the island, Kyousuke and Madoka continue their fun romp, as ``Orange Mystery'' plays in the background. They play hide and seek, hopscotch, and the like. Kyousuke apologizes after bumping Madoka and sending her hand through the sandcastle she built. Madoka poses with a flower in her hair, and Kyousuke shows up painted like a tiger. Tired, the two finally lie down to rest. As the sun grows low in the sky, Madoka suggests ``Shall we go home? Hikaru will be worried that we're late.'' When they get to the beach, though, their boat is gone.
Back at the boat rental store, everyone else is sitting, wondering what has happened to the two of them. Their boat has not returned. Komatsu and Hatta suggest that the two are probably ``making out'' ok. Yuusaku disciplines the two of them for Hikaru, but her concern only for Kyousuke dumps him on the ground. Dunderheaded Kurumi implies that Kyousuke must be all right with his powers, and Manami and their father laugh it off.
Kyousuke lands in the water a little ways off the island. He's used up his energy trying to get to the island and doesn't have enough ``power'' left to teleport back. Back on land, he sees Madoka climbing a cliff. She's trying to see if there's something on the other side. Kyousuke tells her not to risk herself like that, it's too dangerous. She replies that it's her fault that the boat is gone. Just then she loses her grip and falls. Kyousuke jumps off and grabs her as she falls, praying that he has enough ``power'' to zap away the spit of rock that they're falling toward. He does, and the two of them land in the ocean.
That night, beside a fire, Madoka tells him that he was stupid to jump off with her like that. He might have been killed too. Her sandcastle continues to collapse. He takes an apple out of their bag and takes a bite from it. Then, realizing it is their last one, he offers it to Madoka. She looks at the apple and at Kyousuke, then carefully takes a bite out of the same place he did, an indirect kiss, which really impresses Kyousuke.
She asks him if he remembers ``that night'' when they were returning from working at Abcb. This was the night she asked if she could stay over at his place. He does, ``How could I forget?'' She asks him to pretend that she didn't say it. ``Why?'' ``Well, it's the first time I ever said that kind of thing. But... I talked like that, but I feel that I should keep what I have now as a treasure.'' Kyousuke is very touched by this. She then smiles at him, sticks out her tongue and says, ``Could I help it? I used to be a `punk'.'' The waves wash away the last remains of her sandcastle.
The fire cracks, startling Madoka into Kyousuke. They stare into each others eyes for a while and move to kiss. Just then a rescue helicopter flies up with, who else but,y Hikaru. Kyousuke thinks to himself: ``Why does the summer ocean of my 15th year have to end?