The results of the incident were disastrous for the shinobi world. Every single daimyo was on high alert. The Fire Daimyo was ordering Konohagakure to discover the cause behind what had happened. The four other daimyos were sending soldiers to guard their borders in case of an attack from whatever unknown entity just attacked the Land of Fire.
The case was much more serious for the Hidden Villages. Of the four not directly affected, Sunagakure was hit the hardest with the loss of one of their top jonin. The report they received was nothing short of disturbing. The second the jonin crossed Konoha's border he lost his mind and started fleeing. He still hadn't recovered days later and was only shouting about evil figures in the distance and the descent of an Old God of Madness. Despite his grand claims, subsequent surveillance missions showed that Konoha was fine, albeit with fewer shinobi on active duty than normal.
The other villages received similar reports and couldn't help but wonder if a missing-nin's jutsu had gone wrong, considering Konoha was as lost as they were. A few kage even proposed a kage meeting to their advisors but eventually decided against it. Even if this seemed to be a universal disaster that affected everyone involved, nobody could be too sure.
Another strange occurrence reported by jinchuuriki accepted by their villages was the temporary disappearance of the tailed beasts. While the incident occurred, the jinchuuriki couldn't access the power of the tailed beasts, leaving them only as shinobi with large chakra reserves. The only jinchuuriki on truly good terms with his tailed beast, Killer B, reported that the hachibi refused to even show a smidgen of its power in fear of attracting whatever was attacking Konoha. It was also reported that the energy let off by the darkness was barely reminiscent of the kyuubi's power, but only to the extent of feeling vaguely familiar.
This alarmed the villages but they ultimately dismissed it as a coincidence, considering the amount of property damage normally caused by the kyuubi whenever it was free. There was even a direct reference, considering the latest attack was only three years prior. Perhaps someone had stolen the kyuubi's chakra and used it to test a new jutsu. Regardless, it wasn't a tailed beast's attack that created the darkness.
The situation in Konoha was much worse than it appeared on the surface. Hospitals were overflowing and the most skilled medical ninja were out of commission, either inflicted with insanity or still unconscious with their minds heavily damaged. From observations made by the Third Hokage, the stronger a shinobi was, the more likely they were to be hurt by whatever was in the darkness. The damage was never physical but the mental damage was enough to cripple some of the strongest shinobi.
Of those who went insane, there were those that became immensely afraid of the dark, they couldn't even close their eyes without feeling fear. One even went as far as to tear his own eyelids off before anyone could stop him. There were several shinobi who began to believe the visions shown to them were real and sat, awaiting another punishment, believing themselves to be in hell. Many jonin that remained sane had trouble gathering chakra, their mind in frequent disarray as many of the visions shown to them involved the use of chakra. Though sane, they were significantly weakened.
The genin and chuunin fared much better. The chuunin were only exhausted from their initial struggle to stay conscious while the genin were perfectly fine, though both were occasionally plagued with nightmares.
Surprisingly, the group that was hit the hardest was the team of emotionless soldiers commanded by Danzo. The Root members should have been emotionless but were currently perplexed at what they were feeling. They didn't understand why their bodies shook whenever they thought back to the incident. They didn't know why they were hesitant to be alone in the dark. They didn't know why the visions showed the deaths at the hands of Danzo. Several members believed themselves to be a threat to the organization and took their own lives. Danzo himself was almost fine. He was currently bedridden but was otherwise sane enough.
The situation was similar for the Third Hokage. For his strength, he fared far better than any other shinobi in the village. The only noticeable side effect he faced was a slight fear of walls, causing him to move his desk closer to the center of the room. He worked day and night, trying to discover the cause of the disaster. Unfortunately, nothing ever turned up.
That day's events would go down in history, not only for Konoha, but for the entire shinobi world.
Tftc
'Slight fear of walls'. I love it