What if the zombie apocolypse craze reached Gensokyou.
Most characters would be "safe" - youkai are often physical manifestations of a spiritual entity so zombiism probably wouldn't spread. But there
are humans here and there, and zombies are very annoying danmaku users (see Miyako's last spellcard...) and generally malicious (though not intentionally so) so it would still have an impact on everyone.
Reimu may be protected what with her divine powers and whatnot. She would probably set about exorcising zombies and trying to restore things to normal after spending a brief moment shooting down youkai and trying to find how the incident started. Byakuren's probably in the same boat as Reimu. Her faith will probably protect her. As well as Miko.
Marisa may be a powerful magic-user but zombiism doesn't really discriminate. A zombie-Marisa would be pretty terrifying. I could see some final heart-wrenching battle between zombie-her and human-Reimu. Someone needs to write a doujin or something... Alternatively, she could escape to Makai with Alice.
Assuming Sakuya is human (as the canon presents her), she's also at risk. Unlike Marisa however, she's...
a- Surrounded by pretty tough people at all times (eg, Remilia, Meiling, Patchy...)
b- Able to stop time, which would be useful for escaping swarms.
...So she would probably fare better. As a zombie, however, she'd be devastating. Particularly if her ability to stop time remains. Freeze time, shamble up to a few humans, chomp down on their brains, restore time. Bam. Insta-zomb.
Mokou and Kaguya (and Eirin to some extent) are non-youkai but they're also immortal. Mokou, in fact, regenerates very rapidly. Zombiism might not affect them, particularly Mokou, though it's hard to say for sure. They would probably be fine. Eientei's surrounded by a maze of bamboo anyway so they probably won't have much to worry about. I suppose Reisen and Tewi would also fit in there somewhere...
The Youkai Mountain's races would be susceptible. Granted, tengu forces would definitely not go down without a fight (and with people like Momiji who can see/hear/smell across great distances and Aya whose speed rivals that of almost anything else, they should be able to hold the mountain for a while.) Kappa technology would only add to that. But zombies in most zombie apocalypse scenarios are usually infinit for all intent and purpose, so it'd be a battle of attrition. Youkai Mountain would eventually fall and tengu pride would probably lead to all of them being zombified.
Sanae's a demi-goddess. But I hate Sanae. She would make a pityful zombie just like she makes a pityful shrine maiden. Reimu will probably exorcise her while passing her by without slowing down. But Sanahate aside, she's probably fine. Again, she's a demi-goddess. AND she's pretty much surrounded by goddesses at all time. Even if she can become a zombie, Kanako and Suwako would probably find some way to undo it. Sanae'd probably handle things like Reimu, only not as efficiently.
Most people in the Underground are probably fine. Zombies would do poorly in that kind of terrain, plus the burning hells' heat can't be any good for them.
But in the end, aren't zombies and all that also youkai? One way or another, Gensokyo'd stay a world of youkai as it's always been. Just... with zombies instead of lolis.
What if all magic in Gensokyo vanished and every youkai suddenly became human?
