Blood Storm

"Imagine a glass full of water. Then drop two coins on the glass. See the water overflow and spill outside the glass. This is basically it, except massive, deadly, full of malice, and basically, still part of nature."

- Chief Takajo's analogy on the Blood Storm The Blood Storm is a recurring event that takes place in Hero Retold: Kamen Rider Shinobi. It is a metaphysical/mystical phenomenon that infrequently happens at unspecified times around the world, where the waters of the Sanzu River erupts to the world, causing a powerful storm. It is one of the two major events, alongside the Crimson Year, that causes select people to transform into powerful beasts called Nin-Ju.

Overview
In this world's modern understanding, the Sanzu River is a place existing on a separate metaphysical plane, where the deceased human souls exist to be ferried towards the afterlife. Unlike the traditional Japanese beliefs, the souls (coming in the form off glowing balls) are actually submerged to the waters, made up of the Earth's spirit, where it cleanses them of sin, malice, and grief, as they traverse towards the afterlife to be part of the Earth. This, however, mixes the negative elements with the spiritual waters, turning it red. When a huge amount of human souls enter the river at once, the river overflows and the red waters erupt through the several points that connect the metaphysical plane to the Earth (such as Mount Osore). This eruption causes varying degrees of rain, from moderate to a heavy storm, that devastates the said region. Once the storm clears, the waters seep through the region's soil and the Earth filters said negative elements from the waters, revitalizing their potency to cleanse souls, as these waters naturally traverse back to the river to repeat the cycle.

Effects and Aftermath
Though the Blood Storm is a recurring natural phenomenon, this event causes some lasting effects towards the physical world. According to Chief Takajo's report, many of the recorded instances of the Blood Storm leave lands devastated, with some recorded deaths also taking place. In fact, the storm that took place in 2011 gradually caused the shortage of Japan's natural resources, forcing the government to pass the Ninja Act in the first place.

The Blood Storm may have also affected some people that were drenched by its waters. According to Rekka, though not very apparent and immediate, people who have made contact with the waters show potential signs of improved mental awareness, faster reflexes, and somewhat a spiritual connection with the environment, thus creating stories of supernatural people like heroes, gods, and in this case, ninjas. This would later be debunked by Master Gamano one episode later, stating that the waters actually only "unlock" this potential, rather than bestow it to people, and its potential will fade out eventually when not developed upon.

Connection with the Nin-Ju
As stated, the Sanzu Waters pose no immediate effects with humans drenched with them. However, during a separate event called the Crimson Year, the malice that is found in the waters can turn them into monstrous forms called Nin-Ju. When a person under extreme duress is exposed to the red moon's light, summoning the malice mixed through the waters and enveloping them, completing their transformation. At this stage, only a Kamen Rider equipped with the Sanzu Sealing Arts Technique can turn the Nin-Ju back to their human form.

History
The first recorded instance of the Blood Storm is depicted 2000 years before the main storyline, indicated through the Rentaro's ancients scrolls. Since then, many scholars in-narrative have also recorded other instances where the Blood Storm happened. In the latest of Chief Takajo's reports, the most recent Blood Storm took place in the 1950s in the greater area of Japan, that is until 2011 when another Blood Storm hit Japan, which was accidentally caused when Isamichi Konjo's grandfather tried to steal the Shinobi Hyoutans.