nightelf37: Next entry! A Touhou and Super Smash Bros. Ultimate crossover!
A World Remade By Luminous Wings
One day in Gensokyo, Galeem appears out of nowhere at the edge of the Barrier, with a couple of Master Hands. As this wasn't one of hers she pulled from the outside, Yukari lets slip that fact to Reimu and they (and a few others) gather at where it's at and the "audience" soon grows larger, some of them itching to fight it straight away.
When Galeem starts charging up, a few of the yokai seem to realize what's happening and either start pulling back or charging up to it to attack. "Fortunately" for it, Galeem was able to weather the damage before it started shooting out its light attack, first consuming its attackers, among them the oni such as Yuugi and Suika.
Everyone else starts flying and ready to dodge, as per the usual when it comes to Spell Card battles, except this one is for real. Being the boisterous weakling that she is, Cirno decides to attack the light, and is the next to be consumed. Already seeing the seriousness of the situation, Yukari has escaped via her gaps, taking Ran and Chen with her.
Cut to others getting overwhelmed, such as Sakuya stopping time to try and spirit away her mistress, some of those who can go underground (such as Mamizou) do so only for the light to follow, Marisa using her device to counterattack only to be overpowered, et cetera.
In the end, it's down to Reimu and Aya dodging beams as they fly. And then, a gap suddenly opens with enough time to take the former and not any light, leaving the latter in the dust as she's eventually overtaken. And then it shows the beams making it to other dimensions that can be reached by flight, including the Netherworld (which catches Yuyuko off guard as she watched Youmu come in only for Galeem's light to make itself known, but Yukari takes the time to rescue Yuyuko). Oh, and the Human Village gets consumed, too.
But before the attack could overload the inner side of the Great Hakurei Barrier, Yukari (somehow) uses her powers to "safely" redirect it somewhere else, though it unfortunately actually takes out a lot on her. Meanwhile, Ran explains to Reimu why only she was rescued: 1) She's the Shrine Maiden meant to resolve Incidents, and 2) Yukari couldn't risk too many openings lest Galeem's light penetrate her gaps and take this dimension, too.
Once the attack is concluded, another threat comes in the form of Dharkon attempting to enter the new Gensokyo!World of Light. Despite what she just did, Yukari decides to take him on and has her shikigami help her, and Yuyuko assists as well. As for Reimu, she is dropped to the World of Light to find a way to resolve the current Incident.
Only a fraction of the named characters become sealed Fighters while the rest become Primary or Support spirits. For some reason, Reimu gets started off with a Support Spirit of Mima.
The tally is as follows:
Survivors:
Yukari Yakumo (escaped to her dimension)
Ran Yakumo (escaped with Yukari)
Chen (escaped with Yukari)
Reimu Hakurei (rescued by Yukari)
Yuyuko Saigyouji (rescued by Yukari)
All residents in the Moon (not included in Galeem's attack)
Doremy Sweet (escaped to the dream world, but Galeem's actions took a toll on her realm)
Sumireko Usami (snapped awake before Galeem could catch her astral projection)
Maribel Hearn and Renko Usami (not even in the same time frame)
Spirits:
With the following exceptions, who become Fighter Spirits (and eventually rescued to join in the fight), everyone's turned into a Support Spirit.
PC-98 Era: Marisa Kirisame, Alice Margatroid, Yuuka Kazami
The Embodiment of Scarlet Devil: Cirno, Hong Meiling, Patchouli Knowledge, Sakuya Izayoi, Remilia and Flandre Scarlet
Perfect Cherry Blossom: Youmu Konpaku
Imperishable Night: Keine Kamishirasawa, Tei Inaba, Reisen Udongein Inaba, Eirin Yagokoro, Kaguya Houraisan, Fujiwara no Mokou
Phantasmagoria of Flower View: Aya Shameimaru, Medicine Melancholy, Komachi Onozuka, Eiki Shiki
Mountain of Faith: Nitori Kawashiro, Momiji Inubashiri, Sanae Kochiya, Kanako Yasaka, Suwako Moriya
Subterranean Animism: Yuugi Hoshiguma, Satori and Koishi Komeiji, Rin Kaenbyou, Utsuho Reiuji
Undefined Fantastic Object: Ichirin Kumoi and Unzan, Shou Toramaru, Byakuren Hijiri
Ten Desires: Seiga Kaku, Mononobe no Futo, Toyosatomimi no Miko, Mamizou Futatsuiwa
Double Dealing Character: Seija Kijin, Shinmyoumaru Sukuna, Raiko Horikawa
Legacy of Lunatic Kingdom: None. The weaker ones become Support Spirits, while those with the potential to have been Fighter Spirits were in the moon during Galeem's attack and thus were spared.
Hidden Star in Four Seasons: Narumi Natadera, Satono Nishida, Mai Teireida, Okina Matara (Narumi's door to Ushirodo-no-Kuni wasn't closed in time)
Wily Beast and Weakest Creature: Yachie Kicchou, Mayumi Joutouguu, Keiki Haniyasushin, Saki Kurokoma
Immaterial And Missing Power: Suika Ibuki
Scarlet Weather Rhapsody: Iku Nagae, Tenshi Hinanawi
Hopeless Masquerade: Hata no Kokoro
Antimony of Common Flowers: The Yorigami Sisters
Wild and Horned Hermit: Kasen Ibaraki
I would like to say that the overarching threat would unite Gensokyo under one banner, but I know each youkai have their own agendas, and not to mention the Lunar Kingdom might capitalize on this World of Light!Gensokyo and try to take it over. That said, due to the fact that their "food resources" (humans) are stuck as Spirits due to Galeem, Gensokyo's natives would be more inclined to put a stop to him.
Then again, I'm a novice in regards to Touhou lore, so I could be wrong.
nightelf37: Aaand that's it. See ya on Third! Elsewhere.