Basically just a faction that was exiled from an ancient extremely advanced and very spiritual alien civilization. They just happen to have advanced to the point of having energy bodies very compatible with channeling the cosmic force tied to emotional energy. There's a bit more to it than that, mostly stuff related to the hows and whys of the exiling and why they're at war with the Astrals.
So you're telling me they fit in just fine with Kamen Rider.
But keeping it in all seriousness, no characters from the YGO animes will be appearing in this quest, and the only YGO representatives will be the Duel Spirits helping out Rei and fueling her powers, and the certain cooler characters from the sky striker lore.
And, I'm going to shut this down before it gets everyone's speculations way off track, the entity that gave Akemi her wish is NOT one of the many, many eldritch abominations Yugioh has churned out. Though, I'm not too opposed to having them appear as background.
The reason why I chose to make the OCs the main focus is twofold: one, I don't want people to feel like they need to read a wiki page to keep up, and two, the world vote asked for OCs and I plan to deliver.
To be honest, I'm disappointed that both of the protagonists are female. Which is a staple in SV these days. But at least Kaneko's mentor is male, there's that.
As for that, well, I've only been on this site for about two years now and I made my account maybe a year ago, but here's my two cents. Bear in mind I'm only one author, so I might be wrong.
Think for a second about what the three biggest audiences for quests are on this site. Fantasy, anime (usually shonen), and wargaming universes, such as Warhammer. Now I'm going to have to have you picture how many female protagonists you can count from these types of media.
Unless you're really deep into all three of those scenes, I sincerely doubt that anyone could get that list over ten.
I guess is that when it comes to creating quest protagonists, SV is is populated by a sort of niche of people that really wants to see those badass and well written female protagonists, and when you have the extremely open ended process of quest character creation, you just naturally start seeing more female protags.
Heck, even I've got to be aware of the niches present in this quest. I've got some people here for Riders, some people here for magical girls, some people who want to see magical boys, and I've got to balance this universe out where all of them should get to share equal screen time.
Don't worry though, there are definitely a few magical boys coming up in your future,
if Rei looks in the right places.