It is summer in Daten City, and everyone is at the beach. Among the crowd are the resident angels, lounging on their vehicle and surrounded by a group of admirers. The Anarchy sisters complain they should have gone to a private beach, but change their minds upon being offered drinks and sweets respectively. Brief arrives, accusing them of slacking off. According to Brief, the Anarchy sisters were supposed to be helping with the church's beach-house, where Garterbelt is seen cooking Frankfurters and fending off Chuck's attempts to steal one.
To distract Brief, Panty slips off her bikini top and asks him to rub suntan oil all over her back. Brief is left gibbering incoherently at the thought, only to be suddenly knocked away by a familiar red carpet. G-String dramatically bursts from the water, allowing the demon sisters to emerge on the beach, ready for a vacation of their own. Scanty and Kneesocks declare that the beach is private property; when Panty protests, they reveal that they have purchased the beach for five times its stated value, making everyone else trespassers that need to leave immediately.
Unimpressed, Stocking uses Honekoneko to incinerate the property certificate, along with a chunk of Scanty's hair. When Scanty expresses her displeasure over this, Panty leaps off of See Through and challenges her to take the beach by force. However, the demons refuse, claiming that they do not engage in combat during their vacation; instead, they decide to settle the conflict by having a beach volleyball tournament, with Brief as their referee.
The tournament begins, and both teams start scoring points. The game draws everyone on the beach, leaving Garterbelt out of customers and wondering what his charges are up to now. After being hit in the face with an errant volleyball, he gives up on his frankfurter business and sets a betting table instead, disguised as Master G.
The first round eventually goes to the Anarchy sisters, 21 to 18. In response, the demons sisters start using a disguised Fastener as the ball, who shifts away every time the angels' turn comes by. Soon, the demons are leading 12 to 0, and a completely irritated Panty simply shoots the ball, revealing the demons' trickery.
Scanty angrily protests Panty's use of a "dangerous weapon" in the match, while Panty retorts that using Fastener as a ball isn't very funny. Both arguments are reversed when Stocking balls up Chuck and hits him over the net, forcing Kneesocks to cut him apart with her scythe. As Panty and Scanty's argument heats up, Kneesocks tosses the (regular) ball into the air and hits it hard enough to leave a sizable crater on the angels' side of the court.
With a demon tail of pure energy bobbing behind her, Kneesocks declares that she and her sister are going to start using their powers in the game. The angels are more than willing to follow suit, but Scanty ups the stakes by declaring that the losers of the round will have to strip naked in front of everyone. An epic beach volleyball tournament takes place, reaching a level beyond what most of the spectators can see. Brief panics, being unable to see who's scoring, shortly before being caught in the middle of an intense fight between Chuck and Fastener.
The game eventually comes to the last point, with both sides using their best techniques to try and score. Ultimately, the angels prevail, with Panty's final spike leaving a massive heart-shaped dent in the sand (complete with pink heart-shaped ring rising into the air). As Scanty and Kneesocks reel in shock, the Anarchy sisters demand that they hold up their agreement and strip naked for the crowd. Grudgingly, the demons acquiesce, reaching for the straps of their swimsuits...
...and, with a cry of "As if!" they toss bottles of black liquid into the air instead. Two precise revolver shots later, and the ocean is showered with the liquid, causing a whole army of sea animal ghosts to emerge. Scanty and Kneesocks gloat briefly before making their exit in G-String, leaving Panty and Stocking to fend off the horde. Kneesocks muses that she almost forgot their real plan by getting lost in the volleyball match, only to find that Scanty did forget the plan in the wake of the game. Snarling that she will have her revenge on the angels, Scanty slams her fist beside her - and right on top of G-String's self-destruct button, blowing up the vehicle right in their faces.
Back on the beach, chaos reigns: Brief has a Seaweed Ghost wrapped around his head, Stocking is happily writhing in the tentacles of a Giant Octopus Ghost, and Panty has sea star Ghosts on her breasts, an anenome Ghost between her legs, and a clam Ghost on her ear. Meanwhile, Garterbelt counts all the money he made from the betting table, only to be flattened by a whale Ghost falling on his stand.
Several of the Ghosts are misidentified in the English dub; the sea anenome is called a "sea urchin", and the whale is identified as a sperm whale, despite bearing more resemblence to a humpback or a gray whale.