And bringing it all together:
Shadow Clone Jutsu (
Official Version)
This is a B-rank ninjutsu that creates solid clones which are physically indistinguishable from their creator; they possess the same body, appearance, clothing, equipment and chakra.
It was invented by the Second Hokage, Senju Tobirama and was based on his older brother's Wood Clone Jutsu. Said jutsu was the best of its kind; it was identical to its creator to the extent that even doujutsu couldn't see through it, it could withstand more damage than any other clones, was capable of relaying information back to the original real time and had an incredible range.
The Shadow Clone Jutsu was a means of creating a similar kind of clone that any skilled ninja could learn. In fact, shadow clones are relatively easy to create considering the jutsu's rank and only requires a single hand-seal. The reason it is considered jounin-level is entirely because of the chakra cost as it would be uncommon for someone beneath that level to be able to create and maintain a shadow clone for a long enough duration for it to be considered effective. Though some have ingeniously lowered that cost by using living creatures, such as crows, as medium of their clones so that those physical bodies serve as a foundation rather than creating the clone from chakra alone.
Truthfully, the jutsu's surprisingly simplicity is the only reason Uzumaki Naruto was able to learn the jutsu in one night as his desperate training allowed him to generate enough chakra that even he was able push enough of it into the jutsu and produce tangible clones. Said simplicity is also why knowledge of the jutsu is possess by all of the hidden villages existing today.
The jutsu uses chakra to create a physical copy of the user, divides their chakra evenly between them and the clone and then constantly provides chakra to maintain the clone’s existence. Clones are able to generate and mould chakra themselves which means they can use all the skills and jutsu that the original possesses. And even though the clones are formed from chakra, they have been transformed into impermanent matter that so closely resembles real flesh and blood that the differences are impossible to detect. But while the clones possess the same personality and will as the creator, they are ultimately subservient to him and acknowledge him as the original. They share a link with their creator who maintains their existence as the chakra that composes them is finite. It allows him to dispel them, control them non-verbally and maintain a constant awareness of their existence.
Generally, a shadow clone will dispel when struck with a solid blow. But how much damage a shadow clone can survive can depend on the strength of their will and how skillfully the clone was created as masters of the jutsu can create clones that can even withstand multiple stab wounds without succumbing to their destruction. However a lethal blow can only be delayed and guarantees the clone's end. And the clones grow weaker in proportion to however many exist because chakra is divided between them all.
When a clone is dispelled, the chakra that had been divided between them is returned to the original and any existing clones so that their chakra remains evenly distributed. This chakra carries the memories of everything the clone experienced, allowing the original to remember whatever the clone had done as if they had done it themselves. This effect was intended for tricky intelligence gathering such as traversing dangerous terrain and infiltrating enemy territory, allowing the original to collect information from elsewhere without being physically present.
Naruto remained unaware of the memory recall for years as he used his shadow clones almost exclusively for combat purposes, causing all of their experiences to resemble one another and were unconsciously pushed aside in favour of focusing on present events. It wasn't until he was given a situation where he was consciously made aware of the memories that he realised what had been happening all thise time. The unobtrusiveness of the recalled memories is especially true when a clone is killed in action as the experience of their death is muted as a self-defence mechanism to prevent the original's mind from being overwhelmed.
Sometimes the user will possess a seal which is cloned as well, but whatever is sealed inside is not as it exists within a separate space. If creator has a storage scroll containing a single kunai and they create a shadow clone, the clone can use their copied storage scroll to remove the kunai. But if the creator attempts to do the same afterwards, they will not be able to retrieve anything because there was only one kunai. This is especially true of Jinchuuriki who experience a unique phenonemon where their clones possess a copy of the seal as the original that houses the Tailed Beast; they can communicate with and draw upon the chakra of their Tailed Beast and vice versa because they are all connected to the spiritual plane it resides in.
Training Method
It is possible to accelerate one's training by taking advantage of the shadow clone's memory transfer ability. By having them perform the same training as the original and then dispelling, the original has their own experience combined with the clone's so that they gain twice the amount in half the time. With one clone, something that takes twenty years to learn could be done in ten. With a thousand clones, it could be done in a week.
Hatake Kakashi was in fact the first to come up with this training idea, specifically with Naruto in mind.
Originally, the closest thing to training that was ever done with the Shadow Clone Jutsu was to use it as a sparring partner or having the clone reading something to send the information back to the original. Because shadow clones divide the caster's chakra in half and require chakra to maintain their existence, it is a costly jutsu. The original and clone would then use up more chakra from their training which could easily cause chakra exhaustion or even death. On top of that, the accumulation of all that experience has an impact on the original's mind as they suffer the mental stress of possessing extra hours' or days' worth of memories at the same time that can render them unconscious, if not comatose.
This means that the amount of time spent training is far more limited than usual yet even more exhausting.
Most ninja use shadow clones are sparingly and briefly enough that they wouldn't consider the deeper implications of its abilities. And because it's a jounin-level jutsu, most who learn it are already at a level that they likely wouldn't need such an intense training method in the first place.
But Naruto had been using shadow clones since they day he became a ninja as a preteen while most would first learn it until early adulthood at the soonest. He used it far more than anyone else and to much greater effect than anyone else while possessing an immense, ever-growing chakra reserves and equally remarkably recovery which meant that he could create more clones and maintain them for far longer without the threat of exhaustion.
This is truly a training method meant only for Naruto.
Related Jutsu
Multiple Shadow Clone Jutsu - This A-rank forbidden ninjutsu is, in truth, fundamentally the same as the Shadow Clone Jutsu. It uses the same hand-seal to produce the same effect so anyone who knows one jutsu automatically knows the other. The reason that it is officially listed as a separate jutsu is to serve as a warning. Most jutsu can be divided into ones that are inherently dangerous to the caster or ones that aren't but shadow clones are an exception It isn't difficult to safely use several clones yet it is easy to create more clones than the original can manage, causing death by chakra exhaustion. Only those with truly great chakra reserves can meaningful use shadow clones on a huge scale without harming themselves. Thus First Hokage recorded this jutsu in the Scroll of Seals which anyone who learned the Shadow Clone Jutsu was meant to read as well. Ironically, Naruto did this backwards by learning from the record of the Multiple Shadow Clone Jutsu first and thus missed important information about shadow clones such as its memory recall that weren't considered necessary to add to this version.
Shuriken Shadow Clone Jutsu - Invented by Sarutobi Hiruzen, this A-rank ninjutsu combines ninja tools with ninjutsu to multiply the number of shuriken that the user has thrown at the target, each imbued with their chakra, allowing it to increase from one up to a thousand with its use. This removes the need for prior preparation and because the shadow clones are real and not illusions, all the cloned blades are equally lethal. It is more advanced than the Shadow Clone Jutsu because it is significantly more difficult to clone a material object separate from the user in mid-flight along with its speed and momentum, despite needing far less chakra. The jutsu isn't restricted to just shuriken but as the most common throwing implements used by ninja, the name stuck.
Clone Great Explosion - This A-rank ninjutsu allows the user to make their shadow clone detonate in a violent explosion. It destabilises the shadow clone's form as if it had taken a lethal blow, causing it dispel. But instead of just bursting into smoke, the jutsu uses the chakra composing its body to amplify the effect and release a violent explosion. The jutsu can only be used with the Shadow Clone Jutsu. The shadow clones cannot make themselves or each other explode, only their creator can which makes it dangerous, and potentially wasteful, to use when the clone is not within their sight. The detonation also has the unfortunate side-effect of disrupt the memory function so their experiences and anything they have learned is destroyed with their body.
Lightning Release Shadow Clone Jutsu – This is merely one kind of elemental Shadow Clone Jutsu which creates the shadow clone using lightning chakra instead of regular chakra. The A-rank ninjutsu functions exactly like the standard shadow clone until it is dispelled where it releases a powerful burst of electricity capable of paralysing any opponent. But this comes at the cost of being unable to transfer any of its chakra back to the caster because of the elementally recomposed state of its chakra. It is an effective weapon but comes with a heavy cost. And while it has not been witnessed yet, combining such a jutsu with the Clone Great Explosion would make a truly devastating attack.
