The following is a hypothetical scenario in which a Touhou character disappears without a trace in current Gensokyo, and how that would affect the world around them. Many details have been left out for this is merely a proof of concept. If you wish to see a full and detailed fanfiction of this, please say so in a review or request it in PM. The former is easier to numerate.


Reimu disappears without a trace some time after the events of TH15. Assuming TH16 isn't a thing yet, this leads to a new incident that takes its place in the timeline. It is automatically a failure, but the results are catastrophic to say the least. Reimu's two closest cohorts Yukari and Marisa team up alongside a reluctant Alice and act as a sort of police force which cannot match the authority and power of Reimu but is close.

The wild youkai who have not yet befriended Reimu take the disappearance as a queue to run wild, scaring and murdering the residents of the human village. Given their choice of egregious action, the squad has little incentive to keep them alive and goes on an open extermination of wild youkai. This leads to a disastrous psychological effect on the humans as they now have the upper hand on the youkai. They create their own crusade and end up killing even more of them, causing the squad to no longer be able to ignore their uprising. As Yukari had predicted in the beginning, the humans would seize any amount of power they could easily get. Unfortunately, they allowed the humans to have it and now they must take it.

Marisa chooses to leave, and so does Alice. Yukari is alone in her duty to put the humans back in their place. In order to scare them back into subservience but stay well-hidden, she decides to let the Oni that are still left in Old Hell back up to Gensokyo's surface on the condition that they not run rampant like they had in the past. The Oni comply and scare the humans successfully, now acting as restrictions that are much tighter than they were before the disappearance.

Meanwhile, the Hakurei Barrier is starting to fail without Reimu's upkeep. Yukari can't hold the entire thing up on her own and needs to either find a new line of blood to hold the barrier up or indoctrinate an outsider into the Hakurei line. Marisa is immediately turned down despite her willingness for not having the responsibility or dignity required for the job. Yukari distrusts any non-shinto humans, which are difficult to find now that Buddhism and Taoism have taken over. There are ultimately no realistically eligible humans to take up the Hakurei line and so she must take a Plan B. The last available shinto family in Gensokyo is the Moriya line of which Sanae is the youngest and most viable maiden. With little other choice, Yukari allows the barrier to be passed down to the Moriyas who gleefully accept. However, Yukari explicitly prevents them from gaining access to the powers of the Hakurei Orb as it would grant them too much power. The barrier is now renamed to the Moriya Barrier.

The new role causes Kanako to become more power-hungry than she was before. Their previous relative intolerance of Youkai is ramped up to 11. MEANWHILE, the Buddhists and Taoists still have a majority of the human faith and have settled to resolve their difference in the face of the new Youkai threat. Together, they set out to protect the village from any Youkai entering, causing what basically amounts to an exclusion zone where nothing may enter lest it be destroyed. Kanako becomes jealous of the faith they have accumulated and use their excess power to start a turf war with the Buddhist-Taoist alliance. This ends up causing an internal civil war among the humans.

With the Moriyas being OP as fuck now, they manage to recreate the ancient war that brought Kanako and Suwako together, which ends in the alliance being dissolved due to weakness in religious differences, and both being integrated into the Moriya faith. The Moriyas now control the entire human village, but Kanako isn't sated. However, the entire time the humans have been warring with each other the youkai have regained their numbers and now have the Oni by their side. They have the upper hand once again.

The two sides draw ire from each other, and it seems another war is inevitable. Yukari is caught in the middle, forced to choose sides. She has a survival obligation to keep the Youkai population and intimidation up, but at the same time must prevent them from slaughtering and enslaving the humans. As it turns out, her previous solution was merely a band-aid. She ultimately chooses to mediate and command for the Youkai side in the thought that she could suppress the humans and keep the youkai in check without both sides becoming too victorious.

On the other side, we have Marisa who is estranged and solitary after the loss of her friend and being turned down from succeeding her. Her relationship with Yukari is permanently damaged, and she feels the need to teach her a lesson in order to prove her worthiness. She joins the side of the humans as a mercenary. Her friend Alice tries to stay out and acts as a support, being both an outcast from Humans and Youkai alike. She works as Marisa's hidden right hand and supplier of magical goods, a smuggler of sorts who is able to take from both sides and give to the neutral side.

Due to the increasing puritanism among the humans, hate for Youkai grows and the Buddhist wing under Byakuren is put under scrutiny. She and her followers; the youkai she had gathered are exiled from the village and used as scapegoats for the current conflict. The Buddhist wing is now put under new leadership and turns into a more traditional anti-youkai version that Byakuren had originally betrayed.

Everyone from the human village that sympathized with Youkai are exiled as well. Youkai are banned altogether from entering the village. The only youkai left that are not sent out are the Tengu, who act as the Moriya Shrine's special forces, though they are now branded as traitors by the rest of the land's youkai. They are placed on the same pedestal as gods and revered from henceforth as such by the humans, even being officially given ascendant status by Kanako.

The exiled sympathizers eventually find their way into a small and relatively peaceful piece of land far away from the conflict and establish a new village there, which is soon found by Marisa and used as a new base of operations away from the coming storm. The new Buddhists are now basically pirates.

If you're wondering where the SDM is in all of this, they stay well away from it and mostly go into solitary hiding. However, numerous attempts to invade their mansion has forced Remilia to renovate the entire building into an impenetrable fortress. They can't fight back due to being contractually obligated by Yukari, but it doesn't stop them from becoming a the jewel of the conquest. Remilia is approached by the youkai and asked to become a commander, but refuses because of this. The only one who still comes and goes is Sakuya as she is their only viable forager. She must use a disguise to blend into the village and acquire goods. However, they are eventually visited by Marisa who tells them about the hidden village of exiles and tells them to get supplies from there. The SDM now allies itself not with either side of the war but with the mercenaries. They eventually become a defensive and economic powerhouse that fuels the hidden village to become its own paradise.

Meanwhile, the lunar capital is so distraught after their defeat that they don't even think of invading Gensokyo again so soon. Instead, they see the impending weakness and choose to wait out the conflict before weighing their options. The lunar rebels decide to stay out of the coming war and go further into hiding, with Eirin even withholding her services until it ends, effectively embargoing both sides from medical services in an attempt to douse the conflict.

And soon, a war finally breaks out. For the next decade, the humans and youkai would have an all-out and horribly vicious war against each other comprised of countless intense skirmishes. Yukari and Sanae attempt to retain the spellcard rules, but have insufficient influence to uphold it completely. Without Reimu, the rules begin to dissolve and the land turns to classical warfare. Yukari switches her focus to the production of weapons and namely the prevention of it. Sabotage missions against weaponsmiths become commonplace, and the human soldiers eventually start using crude weapons and large numbers to make up for the loss in advanced weaponry. This strains the population and necessitates a draft where every available young adult is conscripted to fight. The birth rate skyrockets with the help of Kanako and Sanae who bless the people with fertility.

Marisa on the other hand becomes an utterly feared monstrosity of war. Her magic adapts from spellcard rules to that of a more classical and destructive nature surpassing that of the Shinki and the leveling of Makai during the events of Mystic Square. Her Mini-Hakkero becomes capable of decimating entire companies with ease, reducing the landscape itself into a smoldering pile of ash in the process. She wins many hard-fought battles and is seen not as human but as a living weapon by all who face her. She essentially becomes Gensokyo's version of the Doom Slayer. Yukari is eventually forced to face her one-on-one. They resolve to use the spellcard rules however, so nothing is destroyed in the process. Marisa emerges the victor.

The war worsens. It eventually becomes so disruptive that even very old, reclusive, and peaceful yet powerful youkai such as Yuuka and Suika get caught in it. Satori, Utsuho, and Rin take the same approach as the SDM and become defensive, with Utsuho thankfully being held back from eradicating the entire surface. Even Tenshi becomes involved even just as a bored punching bag with nothing better to do than beat up whatever she feels like. Yuyuko stays in Hakugyokoro and has her hands utterly full with all of the casualties. Eiki and Komachi become unbelievably busy as well, and Komachi's inability to keep up with the souls causes a repeat of Phantasmagoria of Flower View. This is combination of several incidents from the past becomes known as "The Great Combination" and would be recorded and referenced for centuries to come.

The inclusion of the more powerful youkai causes the war to escalate into unfathomable reaches, to the point where the Moriyas are forced to either use miracles to enhance their armies or find a new source of population to throw at the youkai. Given that the small space they have is unable to hold any more people, they resolve to do the former. They now arm each soldier with blessed items and essentially turn them into a league of magical super-soldier crusaders. Hundreds of people would lose their lives each year, and it would eventually cause the village to go into deep economic turmoil.

Soon, it seemed as if the only thing that could hold back the youkai now was their godlike war hero Marisa. They turn to her, and she accepts their plea. Marisa faces off against Yukari and her generals for at least the tenth time, and they come to the agreement that both sides should not be allowed to win. If Marisa won their last battle, Yukari would take the responsibility to hold the barrier from the Moriyas and give it to her. If Yukari won, Marisa would switch sides and force an unconditional surrender from the humans. Yukari planned to eradicate the human village and exile Kanako afterwards, starting a new one from scratch and make sure this never happens again if she got her way, but she never told Marisa that.

It didn't matter, because Marisa won the battle. She defeats every single general in alphabetical order and then topples Yukari through sheer force of will alone. For the first time since they began fighting, Marisa ignored the rules and killed the generals utterly, forcing the two to go all-out in mortal combat. The fight did not end with yukari being slain, but rather her surrendering after being caught off-guard a single time. Marisa was no longer the kind little girl she once was, but had become a ruthless and opportunistic veteran. What Yukari failed to take into account was just how far she would go to win, and she nearly paid with her life for that. Of course, Marisa never actually intended to kill her because that would just bring an end to everything and ruin the entire point. It was simply a scare tactic.

After Yukari's close defeat, the Moriyas were stripped of their power and it was given to Marisa, who from then on would uphold the barrier. She even takes on the Hakurei name to keep the authenticity. With the barrier weakened from neglect and both sides ravished, humans from the original village began to migrate from their past and into the new village made by the exiles. Some went there, but others went to rediscover Mayohiga and resettle it. After over a decade of constant war, Gensokyo is in shambles but at least at peace. It would take them many years to recover, but when they did they were stronger than ever before.

The Taoists eventually left the old village and relocated to Mayohiga in order to avoid conflict with the Buddhists. The new buddhist wing fell into disfavor and disappeared while the one in the hidden village thrived. The Moriya shrine returned to its normal state, but the immense loss of faith caused its gods to become weak. The Tengu were no longer ascendant but remained relatively the same. Sanae eventually took over completely as one of the sole servants of the shrine. All that is left of it is the old and mostly abandoned village, now reduced to a mere hamlet. Most of the Moriya followers converted to the Hakurei shrine, which Marisa immediately began renovating to attract more people. It would soon see an era of prosperity never imagined, as the people not only came to worship the god that supposedly empowered Marisa, but the girl herself for being a legendary figure.

The Lunar Capital saw the destruction and decided that perhaps attacking was not going to be particularly successful. Given their war fatigue, they simply left the Earth alone for many years to come. Yukari went back into solitude after her defeat. She could not face the rest of her people afterwards, and only appeared to assist Marisa in less important matters while attempting to rebalance the youkai population, which would including sending the Oni back to Old Hell.

And so Gensokyo was whole again. They had at least another lifetime of peace ahead, and so it became quiet once again just as it always should have been. The Great War of Separation would forever be known as one of the worst conflicts in Gensokyo's history, and used as an example to never let it happen again.

And that is what would happen if Reimu disappeared.