Belldandy and Urd's younger sister Skuld arrives on Earth along with reality-bending "bugs" that wreak havoc around the temple.
Summary
Urd steps inside of a hot bath, but almost immediately the water turns cold, and her younger sister Skuld suddenly appears in the bathtub. Urd is not happy having her bath interrupted and Skuld, not expecting her to be there, escapes her wrath through the water.
Keiichi is making no progress on his homework when the cup of tea next to him explodes into a plume of water. Skuld appears but complains about the tea being too hot for her. She and Keiichi greet each other but Urd also appears through the tea, complaining to Skuld about how she can only move through hot water. Belldandy greets Skuld, but when Skuld and Urd argue over Skuld refusing to hug her oldest sister, the eight-legged horse Sleipnir suddenly appears in the room. Skuld puts on a pair of special glasses, and, as she suspected, there's a "bug" with them that she swiftly eliminates with a mallet of hers.
Sleipnir returns to heaven, but Keiichi suddenly becomes two-dimensional, forcing Skuld and Belldandy to go bug-hunting while Urd tries taking a bath again. When he's returned to normal, Belldandy explains that bugs in heaven will rapidly reproduce unless they're being constantly debugged, which in summary means that a number of inexplicable events can occur. Just then, Keiichi vanishes into thin air but lands nearby in the bathtub while Urd is inside. Almost as soon as he gets dried off, he gets teleported again on top of the resident demon Sudaru.
All three goddesses are now in a futile battle against the bugs, as without a debugging program, the bugs will reproduce faster than they can get rid of them. Urd blames the problem on Skuld since she was supposed to be the debugger, but Skuld says that it wasn't fair that she was the only one left to do it in heaven. While Keiichi cheers Skuld up, Urd tries using lightning magic to destroy all the bugs, but she only manages to blow a hole in the roof and surround everyone with even more bugs. Belldandy then catches Keiich's hand right as a hole to an alternate dimension opens under his feet, but Urd are too preoccupied with smashing bugs to help her. Thankfully, Skuld throws one of her homemade bombs into the dimension that seals it up and saves Keiichi, but she says she only did it to step him from touching Belldandy.
Skuld pulls out a large mat with colored circles as part of a game that she "invented" (one that happens to be nearly identical to Twister). Skuld gets Keiichi, Belldandy, and even Urd to play this game and put themselves in compromising positions until they suddenly cause an explosion. Belldandy is delighted to see that the bugs are seemingly gone, but Skuld says that they didn't fix anything because there are still bugs in the Yggdrasil system, something that can't be resolved until she and Urd return to heaven with her.
Urd and Skuld get into another spat over whether Urd had "raised" her younger sister to run to them whenever there's trouble. The resulting explosion causes backup bugs to swarm the temple, and while Keiichi is wrapped up by a talking snake, he contemplates if Belldandy will actually have to leave him.