Dumb ideas

A Certain Magical Tuna(Ver2)

Fandom(s): Honkai impact 3rd( and other parts of the mihoyo multiverse such genshin, star rail, gun girlz, possibly evangelion, and other mihoyo games), Nasuverse(Fate, Kara no kyokai, Notes, Tsukihime, etc), Touhou (takes place in an AU that fuses all 3)

First up let's explain the laws of the our fused Au, I'm keeping things a bit vague because all 3 of the multiverses that have been mixed have strange and confusing laws. The Imaginary Tree and the Sea of Quanta are still here. The [ROOT] is now the literal roots of the Tree, is the point where the infinite possibilities from the Sea of Quanta is given form by the tree. Gaia and Alaya are still here and others celestial object are still sentient. The Will of the Honkai is a higher dimensional being that was born from the Imaginary Tree but is still separate from it, Prometheus(The Ai) is a separate being from the will but it is directly connected to will and can influence and limit the actions it can do within the world of Hi3 .Reality marbles are still things here, the laws of physics are still a result of the common sense of man(basically it's the tulpa effect, the idea that if enough people believe that things work in or behave a certain way, then the world around them starts to work that way). Gaias reality marble still has several layers to it but only 3 really matter here, the human world, the reverse side of the world, and imaginary numbers space(where daemons not to be confused with demons live) Gensokyo is basically an artificially created layer of reality where beings from all the different layers can intermingle, and it can also be used to Access the other layers. Over time with assistance from various gods and other powerful beings Gensokyo has been expanded due to more and more beings moving into it. Also there are no magic circuits Anymore people can increase the amount of OD they can safely use and the quality of the OD the produce through training.

Next we can move onto the timeline before the story starts. The dinosaurs came and went, then the Age of Gods(AoG for short) begun, Sefar came and wrecked the planet leading to the decline of the AoG. Gensokyo is created during the end of the AoG because some of the supernatural beings still wanted to live with humans, the creation of Gensokyo is the same as in normal Touhou. Afterwards things continue into the previous era where things continue in the same way as they did in the Nasuverse after the AoG(none of the beasts manifest), then the timeline starts to diverge when the Honkai starts to show up. Due to Honkai Energy's dangerous supernatural properties it mixes into the ambient mana in the human world, and because Magi and supernatural being utilize the ambient energy it forces the various Magus and the remaining supernatural beings in the human world to retreat to Gensokyo or the reverse, which lead to it being expanded to take in all the new comers. However some particularly powerful being can resist the effect of Honkai energy in the ambient mana and can even make use of it. The Previous Era continues as normal. Then we reach the Current Era and thing continue as normal till the story actually starts. Also because of stigmata and the fact that Honkai beasts continued to show up after the Herrscher Of The End showed up and the fact the there is a bit of Honkai energy everywhere people slowly adapted so the people of the current era wouldnt have as much of a problem with using the ambient energy in magecraft(there would still be risks but it probably wouldn't be as bad as with previous era people), but because there is no one who could currently teach them no one in the current era learn to use magecraft until the story starts.

Before we continue I would like you all to consider something that I feel is rather overlooked by fanfic writers. Kiana has been through a lot, and I'm not just talking about what we see in the game, she has probably been through a lot even before that. Before St. Freya she probably wouldn't even legally exist, but she was able to get into Chiba academy, a school for rich kids, but obviously a school for rich kids would have good security because of who the student's parents were yet she was able to get in suggesting that she would have to have gotten fake legal papers, and she probably wouldn't have been able to use her real last name because the name Kaslana would probably ring  some bells so we know a lot of the info used should have had to be faked. We also know she was able to get into Japan but she was 1st dropped off by Seigfreid in what I think was Siberia, so she would need to get more faked info to cross the borders. She was able to get weapons but there is no way a kid her age, with no legal info would have been able to get weapons legally, even in the world of Honkai where there are monsters and literal child soilders(The valks) they would still probably require licenses and stuff. All of this points to Kiana being heavily involved in the criminal aspects of society, which would likely have affected her and this will affect the 2 possible starting points for the story.

Now both starts could involve Kiana at a different point in time, I imagine that a very young Kiana would probably be kind of like Bronya before she met Mei, young Kiana would probably be quiet, reserved, have trust issues and be traumatized because there are probably a bunch of bad people who would try to manipulate or use Kiana for their own purposes. An older Kiana would on the surface act more like Kiana at the start of the games but below a cheerful mask she would be more cunning, manipulative, and ruthless because of her experience with criminal element, she would also probably be traumatized for much the same reasons as a younger Kiana.

The 1st option is simple, in this option Kiana was put into some kind of situation were she was in danger or under a lot of stress causing the Core of Void to randomly warp here somewhere else. Namely into Gensokyo or somewhere in the Reverse Side of the World like Avalon or the Land of Shadows(we know nothing about imaginary numbers space but considering the fact the daemons are eldritch and incomprehensible beings, their home is probably also incomprehensible). This option basically lets you take Kiana at any point in time before Chiba Academy and drop her into a hotbed of supernatural activity, In this option she would likely be taken in by some one and taught magecraft, who teaches her will likely change her abilities. For example Nerlin could teach her healing or Fey magic, Schatch could teach her primordial runes, or Marissa could teach her how to use emotions in magecraft. You get the idea

The 2nd option starts with Kiana hearing rumors of a ancient artifact which she investigates, thinking she could either use it or sell it for cash and finding some thing that shoves into the moonlit world. For example she could find portals that take her to the Reverse or gensokyo, he could find that stone where Tamamo was supposedly sealed and because Tamamo is an incatnation of Amaterasu Kiana could become Amaterasu's host, she could find Solomons 10th ring and because he would have predicted Kiana finding it he could make it so that who ever finds the ring become Goetia's new master, maybe she could end up awakening Tiamat either becoming her host or releasing her and because Tia could sense Sirin's desire for a family Tia would adopt Kiana. I personally like this start better because I feel it opens up way more options.