The Morisato clan is at the beach after Urd convinced Keiichi to take them. She tells Keiichi that if a couple confess their love under a full moon while standing of the rock of the three sisters, will be a couple forever. Keiichi doesn't believe the story, so Urd threatens to put a sea slug into his swim shorts. Belldandy comes up in a swimsuit and asks if Keiichi is going to go swim. He makes up an excuse for not swimming, but is glad to have come just to see Belldandy in a swimsuit.

Meanwhile, Skuld has created a new upgrade for Banpei called the Banpei Deep Six. It is a combination jet ski and mini-sub with Banpei inside. She's eager to show it off to Keiichi and have him test ride it. He tries to tell her he can't swim as he sits on the device, but Skuld launches him into the water at top speed. He clings on desperately as Skuld remote controls Banpei.

Keiichi wakes up on the shore to find his head in Belldandy's lap. He remembers what Urd said about the rock formation and goes for a walk along the beach with Belldandy. Skuld wants to come along but Urd restrains her. As they walk, Belldandy recalls that their first date was to the ocean. Keiichi remembers and despite not being able to find Urd's rocks, things are going good.

Skuld is demanding an explanation from Urd about what is going on. Urd informs her that she must not interfere with Belldandy and Keiichi, something Skuld has every intention of doing. The couple return and Urd wants to know if he found the rocks. Keiichi confesses that he did not. Urd gives him a speech on grabbing happiness and tells him to try one more time.

Later at their room on the beach, Belldandy gazes out over the ocean and admires the evening view. Keiichi hears Urd's words on the rocks and fantasizes about being alone with Belldandy. Belldandy brings Keiichi back to reality when she notices he is blushing and thinks he might have gotten sunburn. She is worried that Keiichi's mind has been elsewhere and feels that maybe he didn't want to come to the ocean with her. Keiichi immediately replies that he didn't come to see the ocean but to be with Belldandy. She is touched by this, but before things can get romantic, a woman worker at the place they are staying asks them to move Banpei's marine attachment which is parked at the entrance.

For her part, Skuld has built Skuld's Deathtrap Obstacle Course Version 3 in an attempt to make sure Keiichi doesn't cross the line with Belldandy. Urd watches this from afar and is amused. Meanwhile back in their room, Belldandy has taken a bath while Keiichi decides to see if the Three Sisters rock is visible. He runs to the spot where Urd had said it would be visible and sure enough, the rocks are there - the tide going out revealed them. As he rushes back to get Belldandy, he sees a girl who says she's sick on the beach. He offers to carry her on his back to her hotel and is surprised by how much she actually weighs. Actually, she is made of sand and is a contraption of Skuld's, who is quite proud of her trap. Keiichi soon discovers something is wrong forcing Skuld to activate the self-destruct, sending sand everywhere. Keiichi is determined to reach Belldandy more than ever, but sadly hits every trap Skuld sets.

He finally reaches their room and gets Belldandy to return with him to the beach. It is here that he discovers that he has no way to reach the rocks with her, but Urd appears with the solution -- Banpei Deep Six. Belldandy and Keiichi hop on board and race to the rock formation. However, Skuld isn't done yet and sends a command to make Banpei Deep Six dive. Since Keiichi can't swim, Belldandy has to rescue him, flying him out of the water and to the rocks. It is here that Belldandy tells Keiichi she loves him for taking a risk just to show her the moon when he can't swim. Skuld sees this from afar and using the water, teleports to their location. As she does, Keiichi has just finished confessing his feelings for Belldandy. He turns to her and says "I love you", but Skuld is there between them! He thinks that he will now be bound to Skuld, but later, Urd confesses that she made up the story about the rocks.