Taking off after the end of the series, Tsukasa Kadoya, Kamen Rider Decade continues his journey through different worlds along with his friends.
However, a strange anomaly occurs within the dimensions, as different worlds are merging one by one. Wi...
The story begins where we see the scenery of where the Rider War was held.
Then, it focuses closely to a young woman in a white dress, Natsumi Hikari.
As she slowly opens her eyes, she began to survey her surroundings.
Natsumi: This place...
Suddenly, as Natsumi turns around, what she saw behind her is none other than Kamen Rider Decade.
Natsumi: Decade?
Decade turns to look at Natsumi, but after a brief moment, turns to see what lies ahead of her.
As Natsumi turns around again, she sees a group of other Kamen Riders lined up. Which happened to be the second phase Heisei riders.
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Seeing the available riders standing there in order from W to Build, they all stood there as they prepare for a battle.
Then, all the second phase riders began to charge towards Decade, passing through Natsumi as if she's a ghost.
As for Decade, he stood ready for battle as well. But as soon as they reached him, they passed through him as well.
Natsumi and Decade are surprised and confused, but it was cut off when suddenly they saw a figure from afar approaching.
It was what the riders were really charging towards to... another Decade.
The other Decade is all black, while having some gold-color outlines and his eye-visors are blue, overall having the same appearance as the original Decade.
The second phase riders then engage in combat with the Dark Decade.
But as they fight, both sides seem to be in equal strength, following with a bunch of random explosions everywhere.
As Decade continues to see the battle from afar, Dark Decade sees the original and pushes one of the riders out of the way as he charges towards him.
Decade charges as well, and everything ended in a white flash as both Decades are about to punch each other.
As the flash clears, it turns out to be a dream Natsumi was having while sleeping on the couch in her house, the Hikari Studio.
As soon as she woke up, she immediately sat up due to the intense action in it.
Natsumi: *pants and sigh*...A dream?
As Natsumi begins to lay back while sitting, she remembers of seeing the Dark Decade in her dream.
Natsumi: Who was that person? He looks just like Decade...
Yusuke: Natsumi!
Natsumi was cut off when she realizes the voice coming from Yusuke Onodera, Kamen Rider Kuuga from an A.R. world.
