The Mystery Twins Investigate: A Kamen Rider Story is a fusion fic between Gravity Falls and Kamen Rider, specifically Kamen Rider W, written by Michael Ravencroft.
A pair of detectives known as the twins Dipper and Mabel Pines, are contacted for help by someone who claims to have seen a demon in the small town of Gravesfield. The "demon" in question turns out to be fairly harmless, but Foundation X decided to capitalize on this to gain a new follower in the form of Conspiracy Theorist Jacob Hopkins, giving him a Gaia Memory so he can become a Dopans. Thankfully, Dipper and Mabel have the ability to use Gaia Memories to transform into a hero known as Kamen Rider Gemini, in addition to getting help from another new Rider...
The fic, part of the Disney Riders series, can be read on Archive of Our Own here
and on Fanfiction Dot Net here
The Mystery Twins Investigate: A Kamen Rider Story contains examples of:
- Adaptational Badass:
- In the show, Dipper and Mabel were a pair of Badass Normals, but in this fic, they're Kamen Rider Gemini.
- Vee also becomes a Kamen Rider.
- Jacob was a powerless human with no combat experience in the show, but here, he becomes a Dopant.
- Adaptational Relationship Overhaul: In canon, Masha has no idea that Vee is a basilisk impersonating Luz, but they still became friends at Camp Reality Check. In this fic, they're in a relationship together, and Masha eventually learns who Vee really is, as do her friends from.
- Age Lift: Dipper and Mabel are about twenty years old in this fic.
- Bare-Fisted Monk: This is how Kamen Rider V fights, down to calling her attacks like "Rider Punch!" and "Rider Kick!".
- The Cameo: Ford, Stan and Soos appear in a video chat after the former helps them set up a house where they won't be seen by Foundation X.
- Conspiracy Theorist: Jacob Hopkins is this, just like in canon. Dipper, Mabel, Vee, and Miranda, who have actually encountered the supernatural before, don't believe much of what he says.Jacob: The demons have clearly brainwashed the two greatest paranormal investigators of our time! And are planning to use them to help further their coming invasion for Mars! Well, I won’t let that happen! You won’t take the teeth of the people of Earth for your time machines!(Beat)Vee, Mabel, and Miranda: (thinking) What a moron.
- Cure Your Gays: Averted. The reason Masha was sent to Camp Reality Check wasn't because they were nonbinary, but rather, because their parents caught them trying to sacrifice their stuffed animal in the middle of a pentagram.
- Distant Sequel: This story takes place seven years after the events of the final episode of Gravity Falls.
- Establishing Character Moment: Director Keisuke is introduced investigating the same mystery Dipper and Mabel are, and when Dipper says that all Foundation X does is make money from selling weapons, Keisuke retorts by saying that war helps the development of technology, and that Foundation X "is just helping that process along". It's then revealed that he took the time to use a sensor to gather data on the area while he distracted the Pines twins.
- Hated by All: Jacob Hopkins is seen as a nuisance to everyone he meets, and him hunting down Vee as a Dopant only lowers their opinion of him. Even Miranda, the Foundation X agent who gave him his Gaia Memory, lets Gemini get a hit on him instead of intercepting their attack.
- Interquel: Not only are Dipper and Mabel investigating the disappearance of Anne, Marcy, and Sasha, they also an email from Jacob Hopkins, who claims that a demon is living in Gravesfield.
- Mythology Gag: Vee and Camila watch a Kamen Rider movie titled Kamen Rider Eclipse: The Brightest Future, which was heavily inspired by Kamen Rider BLACK SUN. It also ends up inspiring Vee's Rider form.
- Named by the Adaptation: Vee and Masha's friends from summer camp are named Callum and Angie.
- Obliviously Evil: Jacob genuinely believes that he's a hero defending the earth from demons, even when he has the appearance of the terrifying Slayer Dopant.Jacob: So this is the power of a hero!Miranda: Well, it's a power.
- You Are Better Than You Think You Are: When Vee calls herself a coward for running away from the Demon Realm, Camila helps reassure her that she's done nothing wrong.Camila: Vee, you are not a coward. I told you before, you are a brave and strong girl. It took a lot of strength and bravery for you to get away from the people who hurt you and enter a world you knew nothing about. Someday, you’ll see that as well.
