Keiichi and the goddesses take a beach vacation, where Urd urges Keiichi to confess his love for Belldandy at a seaside rock where they are destined to be together forever.
Summary
Belldandy, Urd, and Skuld enjoy swimming in the cold September waters at an empty beach, while Keiichi waves at them from the beach. Urd then gets out of the water and puts a sea slug in Keiichi's face, comparing the two of them because he's not swimming.
The previous day, Urd performs fortune telling for Keiichi, saying that he must go to the beach tomorrow because it aligns with some astrological connection between him and Belldandy that completely goes over Keiichi's head. More importantly, Urd tells him that on the shoreline to the south, there is the Rock of the Three Sisters, a place where people who confess their love for each other will stay together forever. Keiichi initially doesn't believe Urd, but he nonetheless goes along with her idea.
Belldandy approaches them and asks Keiichi if he will swim with them, but Keiichi turns down the offer because he says he's a jellyfish magnet. Skuld then appears and forces Keiichi to try her newest Banpei attachment, Blue No. 6, turning the robot into a submarine that Keiichi can ride atop like a water ski while she operates via remote control. Before Keiichi can bring up the name of the submarine or mention that he can't swim, she activates the device and sends him screaming across the water.
After blacking out, Keiichi wakes up in Belldandy's lap. After telling her he's fine, he gets up to go find the Rock of the Three Sisters Urd mentioned, with Belldandy choosing to follow him. Walking along the shore, they're unable to find this rock, but Belldandy brings up how the scenery reminds her of their first date.
Just before they return, Urd tells Skuld that this time, she must not get in between Keiichi and Belldandy, as it's a matter of destiny, but Skuld vows to do just that. When Keiichi returns, he's startled at how Urd has taken off her top, but he tells her that they didn't find the Rock of the Three Sisters. Urd tells Keiichi that he must try again, urging him to seize his chance for happiness before it's too late, and she mentions how some things are only visible to those who have faith.
In their seaside hotel room, Keiichi thinks about how he should confess his love to Belldandy, but she suddenly asks what Urd told him and Belldandy asks Keiichi if he regrets coming to the beach, seeing that his mind has been elsewhere. He immediately denies it and says he came to the beach to be with her. She's touched by his words, but they're interrupted by the hotel owner who asks Keiichi to move his jet-ski somewhere else. Meanwhile, Skuld prepares some traps for Keiichi to keep her away from Belldandy.
That night, Keiichi heads out by himself to find the Rock of the Three Sisters again. This time, he finds it because it had previously been hidden by the high tide. He heads back to get Belldandy, but he suddenly comes across a woman who claims to be dizzy and lost. Keiichi decides to give her a lift on his back, but she's a lot heavier than expected. However, it doesn't take long for Keiichi to figure out this is a trap by Skuld when the woman suddenly becomes magnetic and Skuld self-destructs her. Undeterred, Keiichi presses on to the hotel, hitting every single one of Skuld's traps (something she pities him for), and finds Belldandy, convincing her to come along with him to a place he found.
Outside, they find Urd having stolen the Blue No. 6 from Skuld and let them use it to race to the Rock. The next moment, Skuld appears asking for the two of them, and Urd points in the direction they're taking. Immediately, she takes out the submarine's remote controller and makes it dive underwater, leaving Keiichi to flail helplessly until Belldandy grabs him and lifts both of them out of the water and onto the rock.
Keiichi apologizes to Belldandy for being a loser who always needs to be saved, but Belldandy tells him otherwise, that despite not being able to swim, he wasn't afraid of the water and wanted to bring here to see the Moon, demonstrating precisely why she loves him. However, Skuld sees what's happening from the shore and impulsively moves through water to appear next to them, and the moment when she leaps in between them is exactly the moment when Keiichi tells Belldandy that he loves her back.
Keiichi is flustered that he managed to mess up his prophecy with Belldandy, but back at the hotel Urd tells him that she just made all of that up. The only silver lining is that Belldandy seemed happy after everything that happened.