This is the first episode of Kamen Rider: Equestria Heroes.
The episode starts with a prologue talking about the Rider War, and Decade's part as the Destroyer of Worlds, and the eventual hero. We then see another depiction of the Rider War, but with a mysterious girl in a purple cloak watching the events, similar to the nightmare Natsumi Hikari has in the first episode of Kamen Rider Decade, only the riders Decade is fighting are dark shadowy versions, and Decade is in his Complete form. Upon defeating the last rider, Decade looks at the girl, and a gust of wind blows her hood off, revealing her not to be Natsumi Hikari, but rather a girl with straight hair in purple and pink streaks. As the scene ends, the girl says "Who are you?", with Decade replying right when the scene cuts to black, but it's not clear as to what he says to her.
We are then introduced to a girl named Twilight, who falls out of bed after a nightmare she had. A young boy named Spike (who is later revealed to be her adopted brother) comes to her aid asking if she had the same dream again. Twilight just nods her head. Spike then insists that she should tell their parents about it, only to have Twilight say that she doesn’t want anyone to think she's crazy, especially after she lost her memory two months ago. It's not revealed how this happened, and it's assumed that is was a spontaneous event.
Regardless, Spike and Twilight try to go about their day normally. Spike comments how Twilight never seems to have any friends, only to have Twilight scold him about she just knows she had friends once, and becomes sad upon saying that, knowing she can't remember them.
It's at this point, looking through a mall, which they come across a camera shop. Spike could have sworn it was a tea shop not to long ago, but shrugs it off saying that things change it the mall all the time. However, in the window is a strange twin lens reflex camera that catches Twilight's eye. For some reason she is drawn to it, and purchases it. Spike questions her impulse to buy it, but Twilight again scolds him, saying she want to take pictures so she has some form of memory in case she looses it again.
On their way home, they are then attacked by strange creatures. Twilight and Spike run, only to have Twilight trip. Just as the monsters close in on them, everything freezes.
As Twilight and Spike try to make sense of what happened, a young man appears before them. He explains that he was looking for Twilight for some time. When Twilight asks who he is, he simply says...
"I'm just a passing through Kamen Rider."
The same line Decade tells Twilight in her dream.
With Twilight wanting to know more about what's going on, Tsukasa Kadoya (as Spike demand he give them a real name) explains that their world is nothing more than a fragment, and it's creation was the cause of Twilight's memory loss. There were once two worlds, that of the humans, and that of the ponies. Apparently, someone tried fusing the two together, and ended up shattering them completely, causing many "Fragmented A.R. Worlds". Twilight is also a fusion on two personas, that of a human high school student, and a pony princess. Somehow, unlike the others, both halves rejected each other, and Twilight was rendered without a memory at all. When asked how he knew this, Tsukasa tells them that he is from neither world, but rather from another series of worlds that somehow became linked with theirs when the two shattered, and the cause was something from the site of the Rider War he was part of, although he cannot confirm what it was, or who caused it.
Because he is unable to wander the worlds on his own, being they were not part of the worlds he was from to begin with, he asks Twilight to take up the search in the Fragmented A.R. Worlds, giving her his Decadriver and Ride Booker. Upon handing them to her, Twilight, and in some way, Spike, regains her true memories of both their personas (although the pony princess one is the most dominate in Twilight). Tsukasa also gives her a warning. Because she now has his powers as Decade, she could potentially destroy the worlds in order to connect them; also saying that she may run into other riders who "emulate" ones he's encountered before, which will make her task harder. However, Twilight says it would never come to that, as she is sure that the "Elements of Harmony" would make it so that the worlds will not be destroyed. Tsukasa comments on this, saying that if what she says is true, maybe the Rider War would have never happened.
Once Tsukasa takes his leave, time resumes, and Twilight and Spike still find they have to deal with the monsters that attacked them before. However, with the Decadriver and Ride Booker, she transforms into Kamen Rider Twilight, and defeats the monsters with ease.
Upon returning home, Twilight decides that she needs to find a way to travel to the other worlds, but decides to let her older brother Shining Armor know what's going on. But, when she tries to call him, his phone is disconnected. Fearing something may have happened to him, she decides to go to the neighboring city to see if he is okay.
- Twilight Sparkle/Kamen Rider Twilight
- Tsukasa Kadoya/Kamen Rider Decade