Black Egg Affair

The Black Egg Affair (黒卵の件, Kokuran no Ken), known by its victims as the Foremost Atrocity, occurred around the same time of the Withdrawal of the Fourth Branch and was long considered to be the motivating factor for the split. Ten school-aged children, all of shinobi descent and most of which who came from long lines of proficient sensor nin, were captured by a kunoichi by the name of Fujiwara Nanaho and imparted with a Cursed Seal. The original purpose of the seal was speculated to boost a ninja's chakra perception beyond natural levels in order to create more elite sensor nin; however, complications arose in both the subjects and the seals themselves that resulted in the death of two victims, mass chakra-path traumatization of the remaining eight, and the subsequent ire of three of five Elemental Countries. Fujiwara Nanaho's involvement criminalized both herself and her clan, and she was branded and exiled by her fellow branch members for inhumanity.

In an effort to increase the Fujiwara clan's success in feudal skirmishes, Fujiwara Nanaho began researching the benefits of sensor-types in battle. Believing that the addition of sensors would be to the greatest advantage of the clan, Nanaho began compiling data on chakra perception and sensor bloodlines. Due to the Fujiwara clan's chronicled disadvantage in chakra capacity, Nanaho concluded that the most effective option would be to artificially expand the natural range of a ninja's chakra-sensing capabilities, using sealing techniques as a proxy. Her initial pitches were refused by the acting Clan Head for their potential danger to the wearers; the Fujiwara were also famous for their high output of chakra path mutations, so the procedure was considered to great a risk.

Undeterred, Nanaho decided to take matters into her own hands. Using confidential clan records, she identified descendants of the Fujiwara far enough removed to have joined or grown up in separate clans or countries. Through these distant members, Nanaho tracked the family trees of their sworn Countries' sensor-nin and chose the most likely candidates for her "program"; these individuals later came to be known as the Black Egg 10 through both her study notes and through the mission reports of tracking teams. These candidates, all in their first three years of the academy, were spirited away and taken hostage in a covert base in the Land of Snow.

Nanaho branded the 10 with a reverse-engineered Curse Seal designed to expand the victim's chakra pathways and increase chakra sensitivity. However, in order to prevent herself from being detected, Nanaho had designed the seals with a closed loop of activation chakra that fed off the host's own reserves. The pattern she had used left the seals highly unstable, resulting in massive trauma to her subjects' chakra paths and a hypersensitive perception factor. The youngest of the 10 died immediately upon receiving the seal and another member followed shortly after, within ten minutes of people branded. Three more suffered severe cerebral trauma resulting in epilepsy.

All eight of the surviving 10 were bedridden for months after rescue, recovering from severe and debilitating overstimulation. Nanaho was charged with illegal experimentation, medical malpractice, and the Fujiwara's personal charge of "Inhumanity". The last of these charges resulted in her exile from the clan; Nanaho was stripped of all rights to her surname, branded on both cheeks, and had her chakra signature removed from the Clan wards. She was sent away from the compound and ostracized by any of her previous family members she came across.