The term "Hyakki Yagyō" first appeared in Japan in the Uji Shūi Monogatari, in a story titled "Shokubunsha Hyakki Yagyō ni Au Koto." It is said that the spaces inhabited by yokai and humans overlap. Humans are active during the day, while yokai appear at night. As night falls and the streets become deserted, various grotesque yokai emerge, marching along the main roads like a festival procession, with ferocious faces. This phenomenon is known as "Hyakki Yagyō."
In Japanese "setsuwa" (tales), more complete descriptions of Hyakki Yagyō emerged, influencing painting and theater. For instance, Toriyama Sekien's "Gazu Hyakki Yagyō" (The Illustrated Night Parade of a Hundred Demons) even lists the origins of these yokai. Many of the prototypes for these hundred demons originated from China and India.
The time period for Hyakki Yagyō, "Ōmagatoki," refers to twilight, a supernatural time. Twilight (5 PM - 7 PM) and dawn (3 AM - 5 AM) are considered by Japanese Onmyōdō to be the times when supernatural beings are most likely to appear.
In reality, on the day before the start of spring (Setsubun), Japanese people typically discard old and unused items outside their homes and burn them, or hold bean-scattering rituals to ward off evil spirits. It is believed that eating a number of beans equal to one's age will ensure a year of peace and health, leading people to eagerly collect these beans.
However, after the resurgence of spiritual energy, Hyakki Yagyō became a real, unstable, top-tier natural disaster (ranging from A-class to SSS-class), occurring every three to seven years. There have also been cases where it occurs only once every few decades. The longer the interval between two Hyakki Yagyō events, the more concentrated the accumulation of "ki" (spiritual energy) becomes, leading to greater destruction during its eruption.
While the harm caused by the wandering evil spirits of Hyakki Yagyō is one aspect, the truly long-term detrimental effect on ordinary people is the pervasive miasma of "ki" that blankets the land.
Ordinary people who inhale this "ki" suffer a permanent decrease in their resistance (reduced magic resistance). While alive, they are highly susceptible to harassment, attachment, and even death by "ki"-infused creatures. After death, they are very likely to become new wandering spirits.
To prolong the time between Hyakki Yagyō events and reduce the damage caused by each occurrence, Japanese people, after decades of exploration and adjustment, have sealed the eight "keys" that trigger Hyakki Yagyō (gourd, broken sword, shakujō, folding fan, naginata, round fan, broken horn, fox mask) in Kyoto, Miyagi, Kumamoto, Sapporo, Tokushima, Tokyo, Nagano, and Fukuoka respectively. These seals are jointly maintained by various civilian supernatural organizations such as Kiyomizu-dera Temple, Kuzu-ryū Shrine, Hachiman-gū Shrine, Hase-dera Temple, Tenpuku Sencha Shrine, and Kōtoku-in Temple. The seals are periodically released to trigger these disasters, with the government taking preventative measures and diverting the events to sparsely populated areas.
Under normal circumstances, Hyakki Yagyō triggered by these operations are typically S-class natural disasters with A-class level of threat. (Previously, a disaster of this magnitude, almost S+-class in power, occurred within a prefectural capital, resulting in S-class damage.)
This time, the hastily organized Hyakki Yagyō has a maximum power of A-class and is confined to the central area of Tokyo. Therefore, it should not be a concern for the rebels.
However, the involvement of Mochigawa has escalated this disaster by at least two threat levels, pushing it close to SS-class.
For Mochigawa himself, most of his powers and strength as a "oni king" have been awakened. His combat power is essentially capable of suppressing those at the eighth stage and engaging those at the ninth stage depending on the situation.
This is also why Shuten Dōji, although not an SSS-class oni king himself, was able to fight three eighth-stage cultivators simultaneously due to prolonged immersion and enhancement by "ki." (Furthermore, Otoko is not strictly a combat-oriented supernatural user, so this was a misjudgment by Suikin.)
As the miasma of "ki" advances, the rebels find their resistance increasingly futile, even with the aid of supernatural users.
Behind the Hyakki Yagyō procession, Zhang Hanshan, holding the Golden Dragon Shakujō, with the generals Zeng and Sun leading the way and He Lanxin covering the rear, proceeds east along Heian Street, absorbing the residual "ki."
The Golden Dragon Shakujō emits a gentle glow. Countless purple wisps of "ki" and golden points of light slowly enter the shakujō. The eight golden rings clink against each other, producing a clear and pleasant sound. This purifies the souls of those who have inadvertently inhaled "ki" and repels hidden yokai.
"Generals, am I doing this correctly?" Zhang Hanshan asked, gently shaking the shakujō.
General Sun, who was clearing the path with a chain, said, "You are doing very well, Little Venerable. With time and practice, you will surely catch up to the Venerable."
The other general, Zeng, was more reserved but nodded in agreement.
He Lanxin quietly observed Zhang Hanshan's remarkable power, sighing inwardly.
"This feeling... it's definitely the response of Takamagahara!" Toujou Kiyoshi's face was contorted with frenzied ecstasy as he watched the Kusanagi-no-Tsurugi and Yata no Kagami slowly take shape.
"How is this possible..." Itagaki Seishirō and Prince Noriyoshi looked astonished. After all, the Three Sacred Treasures were merely legendary items. The appearance of two of them was unbelievable to anyone.
As the golden katana and purple jade mirror materialized, the breathing of all three present quickened.
"These... are truly the Three Sacred Treasures..."
"No," Itagaki Seishirō seemed to discern something. "These are projections of the Three Sacred Treasures. Their power should be discounted... but they are still formidable..."
Toujou Kiyoshi reached out and grasped the Yata no Kagami, immediately feeling a powerful yet gentle spiritual energy spread throughout his body via his spiritual meridians.
"This spiritual energy..." Toujou Kiyoshi's eyes glazed over, feeling a premonition of a breakthrough in his cultivation. Driven by his desire for power, he instinctively looked at the Kusanagi-no-Tsurugi.
Just as he was about to grab it, Itagaki Seishirō quickly stopped him, his face grim. "Toujou Kiyoshi! Remember your promise!"
A murderous glint flashed in Toujou Kiyoshi's eyes from behind his glasses, but he lowered his head to conceal it. After a moment of silence, Toujou Kiyoshi said, "Of course... General Itagaki, as you are to become a national general, the Kusanagi-no-Tsurugi may be quite suitable as your sword!"
Itagaki Seishirō gave Toujou Kiyoshi a deep look, then let out a cold laugh and turned to take the Kusanagi-no-Tsurugi. In his opinion, Toujou Kiyoshi did not yet possess the strength to betray him.
However... Itagaki Seishirō had underestimated Toujou Kiyoshi's madness.
Just before Itagaki Seishirō could grasp the Kusanagi-no-Tsurugi, a flash of silver light struck, decapitating him.
A hint of joy and pleasure remained on Itagaki Seishirō's face.
Prince Noriyoshi smoothly sheathed his sword and bowed to Toujou Kiyoshi. "Grandfather, this plan has succeeded."
"Good, Noriyoshi, well done..." Toujou Kiyoshi, from an angle Prince Noriyoshi could not see, slowly manipulated the Yata no Kagami. "Noriyoshi, take your reward..."