[FairyKing]

I don't have all the details worked out, but I was thinking about the possibility of toku set in worlds other than present-day Earth, and that grew into this idea I call Kamen Rider Mars!

It's the story of the twin Akahoshi brothers, Fumito and Daichi, nicknamed the "sons of Mars" because they were the first humans to be born in a Mars colony, the sons of important scientists. They were both raised to feel like Mars's future was in their hands, but they reacted to that "destiny" in very different ways: Fumito stayed in Dome City One and entered politics, eventually becoming governor of the whole colony and quite influential in Martian politics as a whole, while Daichi left to explore Mars and help people in need, and gradually became known as a folk hero.

But when a secret organization calling itself Exterra kidnaps Fumito to experiment on, Daichi is called home to Dome City One to rescue him, and Mrs. Akahoshi gives him the Mars Driver that she and their father built before their father went missing, allowing Daichi to become Kamen Rider Mars Deimos! But mysteriously, Exterra also has a Mars Driver, which Fumito takes during the escape and uses to become Kamen Rider Mars Phobos! That's right, Kamen Rider Mars is not one Rider, but two!

Basically, I'm taking the concept of the second Rider getting their own plot instead of just being the main Rider's partner to its logical extreme, and saying they're both the main Rider. Similar to how not all Riders use their full titles in the series (like Wizard just being called the "ringed magician" and all the Riders from Gaim being called Armored Riders), they might shorten their names to just Kamen Rider Phobos and Kamen Rider Deimos, but officially they are both Kamen Rider Mars.

Together, the twin Mars Riders fight to save the people of the colonies from Exterra's sinister experiments. Just one problem: The brothers may have been best friends as kids, but now they don't get along at all! Fumito sees Daichi as an undisciplined showoff who rushes recklessly into things and then runs away from the consequences, while Daichi sees Fumito as a stuck-up control freak who never acts without a complicated plan and expects everyone to follow his lead.

Their relationship gradually improving, and the many arguments they have along the way (from silly things like "who says their catchphrase first?" to deadly serious like "do we endanger a whole group of people to save one?"), would drive a lot of the show's comedy and drama.

The third Rider is a mysterious young woman named Ari, who seems emotionless a lot of the time but sometimes shows hints of being shy, awkward and sweet. Like the brothers, she was born on Mars, but she has no idea who her family is and might even be a clone. She was raised in secrecy and isolation, given barely any human contact and trained to be a weapon. Exterra brings her out of hiding and gives her the DiscorDriver which she uses to become Kamen Rider Eris!

But after seeing how the brothers still love each other even when they're fighting, Ari runs away from Exterra and stumbles her way to Dome City One. Mrs. Akahoshi finds her and brings her to her house so she'll have a place to stay, and Ari reveals that the one thing she wants most is a loving family, so Mrs. Akahoshi basically decides to adopt her. The brothers are surprised by this at first, but she actually brings some much-needed calm to their family.

I don't know what their collectables/forms or arsenal should be yet, but I figure their suits should be inspired by space suits (but different from Fourze), maybe with red eyes and accents for Phobos and blue for Deimos? And it would be cool if they used identical weapons with 2 modes, that transformed in a way where it was mainly red in the mode Phobos favors and mainly blue in the mode Deimos favors.

In case you couldn't tell, the big theme of this season is family.