Jujutsu(Base): In this world, all but a few humans possess a form of spiritual energy known as cursed energy, which is produced when feeling negative emotions such as anger, fear, or grief. Most humans, however, have no control over this energy. As such, it leaks freely from their body, causing it to congregate and coalesce into cursed spirits. There are an incredibly rare few who are born with the ability to control this cursed energy, though – people known as sorcerers.
You are now one of these sorcerers, granting you the ability to manipulate your own cursed energy. While you aren't capable of anything particularly special with this alone, there are a good number of benefits to this. For one, you are able to perceive cursed spirits and other spiritual entities with your senses, something usually impossible for non-sorcerers without specialised tools. Additionally, you're able to channel this cursed energy into your body to enhance your physical abilities to superhuman levels, with greater results coming from greater investments.
The above are but the most basic of uses of cursed energy – for more specialised and powerful ones, you'll need cursed techniques. With this alone, you're capable of some basic barrier techniques, which let you create (often spherical) walls of cursed energy to close off an area. The most common form of this is a curtain: a large, pitch black sphere that prevents those outside the barrier from seeing what's happening within. Barriers can also be hardened to make entry or exit more difficult, though be aware that the more difficult it is to leave a barrier, the easier it is to enter and vice versa. In addition, you also have the capability to summon shikigami: creatures resembling cursed spirits created from your cursed energy. These require an intermediary such as a talisman to summon, tend to be rather straightforward in terms of abilities, and won't be particularly strong, though this may be changed with some practice.
Unfortunately, aside from barriers and simple shikigami, most cursed techniques are innate, and as such cannot be learned. It's also entirely possible for a sorcerer to be born without a cursed technique, and as such you will not receive one from this alone. The Cursed Technique section later on will allow you to purchase one for yourself, though certain other, riskier methods may also allow you to obtain one.
Tsukamoto: A small cursed corpse, taking the form of a small stuffed doll bear with boxing gloves on its paws and a rather ugly face. Its main purpose is to help sorcerers learn how to use cursed energy. As long as it is supplied with a constant, steady stream of cursed energy, it will remain asleep, snoring peacefully. The moment that flow is interrupted, be it by giving it too much or too little, it will awaken and start punching those closest to it until it receives energy once again. The punches definitely hurt, but they aren't strong enough to seriously injure anyone. Usually, it's set to only require a low amount of cursed energy at first but will gradually increase its demand, training the user to maintain a higher output.
Kei Conservation: You have learned how to make do with less. You require 25% less energy for all techniques, this is increased to 50% for techniques that require constant energy use.
Master Swordsman: You possess the incredible skill of a seasoned swordsman. Your reflexes, precision, and technique are at a level that only the most dedicated of sword fighters can reach. Whether you're armed with a katana or any other blade, you can easily slice through enemies with devastating accuracy. With every swing of your sword, you can precisely cut through opponents or deflect incoming attacks, leaving your enemies in awe of your skill. This is the foundation of Atomic Samurai's incredible swordsmanship.
Keeping Promises: Binding vows were already brought up previously, but it's worth noting that placing restrictions upon oneself is only part of what's possible with this aspect of jujutsu. No, binding vows can also be made with others. This often takes the form of a contract between two parties, where both agree to a certain set of conditions, most often certain actions they must do for the other party. Unlike in a self-imposed vow, however, the penalty for breaking a binding vow with another is much more harsh. Though the exact details of what will transpire will vary from vow to vow, the punishment is severe enough that even the most powerful of sorcerers and cursed spirits do their utmost to honour such agreements.
Usually, these require that both parties are capable of manipulating cursed energy. You, however, can apply the principles of a binding vow with anyone, regardless of whether they can use jujutsu or not. When you make an agreement with someone or a group of people, you can choose to make the terms nigh-inviolable as described above. All parties involved will understand that breaking the terms of the contract will result in them suffering severe penalties, far worse than any gain they might have received from not honouring the vow. Naturally, this isn't a one-sided thing: you, too, will face consequences for breaking such a deal. However, it's important to note that abusing loopholes in the vow's wording doesn't count as breaking it. If you agree to kill someone, for example, killing them and then immediately reviving them afterwards is completely acceptable unless explicitly agreed otherwise.
Healer: Cursed energy is capable of a great many things, but it does have its limitations. As an innately negative form of energy, it is impossible to use it to heal oneself or others in its base form, for instance. Yet there is a way around this: a method known as reverse cursed technique. By multiplying cursed energy against itself, it instead becomes a 'positive' form of energy, and thus can be used to heal. While this sounds simple, it's a rather complex thing in practice, with many talented sorcerers being unable to grasp the process.
You, however, don't struggle with this at all, being a true master of reverse cursed technique. The most obvious benefit this gives you is the ability to heal yourself as well as others through physical contact. Though you may leave some scars behind for more serious wounds, with this you're capable of healing anything from cuts and bruises to slit throats and missing limbs. The more severe the injury and the faster you wish to heal it, however, the more energy will be required, and there are certain things that are more difficult to cure. Poisons, for example, take a lot of concentrated effort to neutralise, and damage to the soul cannot be healed at all.
This is only one use of reverse cursed technique, though: significantly, it can also be used in conjunction with one's cursed technique. By powering one's cursed technique using the positive energy generated through reverse cursed technique, its effect becomes reversed. A technique that pulled people closer would be made to repel them, while one that weakened gravity in an area would amplify it instead. While any user of reverse cursed technique would be able to use this, purchasing this perk allows you to apply this reversal of effects to any other supernatural powers you may possess.