Cursed Energy
Cursed energy is a power source aligned with negative emotions used by sorcerers and curses to fuel their jujutsu. This energy is born from negative emotions such as grief and anger. While these negative feelings are common in human society such that almost everyone possesses cursed energy, if this amount is higher than a certain degree, it grants the person the ability to see curses, which is very rare among the human race.
Humans with an above-average level of cursed energy can see curses and jujutsu, while jujutsu-related items such as cursed tools, cursed objects, and cursed corpses all contain cursed energy. The (typical) minimum requirement for a human to be considered a sorcerer is the ability to see curses. In extreme cases, humans will gain the ability to see curses when their life is in danger. Human senses are heightened when their life is in danger because of the instinctive fight or flight reflex, so this concept also applies to why normal humans can suddenly see curses in a life or death situation. Moreover, this amplifies someone's ability to sense curses because a normal human's cursed energy will rise if their life is in danger of being cursed, allowing them to perceive it.
Alongside emotion, risk is a key factor that can affect cursed energy - the greater the risk to the user, the more their cursed energy will react. Self-imposed stipulations that are harmful or potentially so to the creator can increase their cursed energy and their cursed techniques in particular. Similarly, divulging their techniques to their opponent can also achieve this effect. A jujutsu practitioner can increase the overall power of their individual cursed techniques by self-imposing further restrictions that force more conditions on the user. Although extreme, it is believed that the fastest way to raise one's level as a sorcerer is a Binding Vow with their life as the trade off. Due to the negative emotions induced by potential repercussions, cursed energy grows in response and makes the cursed technique more effective.
Using jujutsu leaves residuals of cursed energy behind. Residuals leave spectral footprints that can be used to track the user. Someone can even be identified by the residuals from their jujutsu. Expert sorcerers can be trained to cover up their residuals. The ability to detect cursed energy and understand its flow can be honed, but many cursed spirits are capable of hiding their presence the same way a sorcerer does.
Cursed Spirits (Curses)
Cursed spirits, also referred to simply as curses are a race of spiritual beings manifested from cursed energy as a result of the negative emotions that flow out of humans. They bring harm to humanity as apparitions manifested entirely from cursed energy and are consequently the primary targets of jujutsu sorcerers. Since their bodies are composed of cursed energy, cursed spirits are invisible to non-sorcerers.
The emission of cursed energy from humans continues to accumulate until a cursed spirit is born from the collective negative energy. Curses born with strong feelings directed toward a certain aspect are especially strong. For instance, more powerful curses are spawned from negative sentiments such as humanity's fear and anger directed at cursing a certain aspect of the world, like natural disasters. To get more specific, curses are created when cursed energy leaks from humans as a result of their human emotion and builds up like until a cursed spirit takes form. By this nature, populated locations such as schools and hospitals are hot spots for bearing curses because many negative emotions are associated with memories of those places.
Although the origin of curses and jujutsu is largely unknown, it's widely accepted that curses have always existed alongside humanity because cursed energy comes from negative emotion. In the modern-day, the number of unexplained deaths and disappearances in Japan exceeds ten thousand annually. The true cause of high unexplained death and disappearance statistics is the influence curses have on normal society. However, their existence has been kept secret from normal people as they are invisible to them, so jujutsu sorcerers act in secret to repel the threat of curses.
Since the metaphysical existence of curses makes it impossible for regular people to perceive or touch them, humans who have been cursed can only tell they have strange symptoms without realizing a cursed spirit behind it. However, non-sorcerers whose lives are put in danger by a possessing curse may gain the ability to see it in that life or death situation. Curses come in all kinds of grotesque shapes and sizes, but they always tend to linger around their point of origin and instinctively curse humans and are most stable while possessing an item, though some become a cursed corpse when possessing an inanimate object.
Following the general rule of jujutsu, a curse must be exorcized using another curse, so they can only be eliminated by humans using cursed energy. A fatal attack using cursed energy will cause the cursed spirit to disappear completely, but this does not apply to curses who have been incarnated using a flesh and blood human vessel. Curses that are too powerful to be destroyed must be sealed away using a constraint. If a vengeful spirit that is cursing someone is too powerful to exorcize, millions of figurative "knots" of cursed energy must be slowly analyzed and undone one by one. The cursed can do so by learning to master channeling the cursed energy being used to curse them.
Classifications
Rank/Grade: Sorcerers, cursed spirits, and cursed tools are ranked on a grade scale to help quantify overall power and potency. This ranking helps match sorcerers with missions involving curses of the same relative level. The higher the grade, the stronger and more dangerous it is. For instance, they have explained the ranking of cursed spirit with the following:
- Grade 4: "A wooden bat is enough."
- Grade 3: "If you have a handgun, you can rest easy."
- Grade 2: "Close call with a shotgun."
- Grade 1: "Even a tank might be insufficient."
- Special Grade: "Cluster bombs might work."
Vengeful Cursed Spirit: Created when humans become a curse after death. Those whose deaths are cursed have the possibility of having their spirit corrupted and transformed into a vengeful spirit. Sorcerers have an increased chance of turning into a curse after death, but this can be prevented through jujutsu.
Imaginary Vengeful Cursed Spirit: Manifested from the cumulative fear of the masses, like when many people share an image of fear, such as famous yokai or ghost stories like the Nine Tailed Fox. Since they are widely feared by sorcerers, they are classified as such to distinguish them from other curses.
Disease Cursed Spirit: Plague and general sickness are concepts constantly cursed by humanity, resulting in powerful disease curses. These types of cursed spirits can use cursed techniques to infect humans with their respective diseases to curse and kill them.