The Spirit Sword (霊剣 Rei Ken?) (translated as Aura Sword) is the signature technique of Kuwabara. Its typical form is that of a sword comprised of fire energy, and the technique's cutting power is based on the amount of energy put into it by its user.
During the tournament held by Genkai, Kuwabara fought Musashi, a demon hunter wielding a holy wooden sword. Picking up a piece of broken sword plus the anxiety of the moment allowed Kuwabara to manifest his spirit energy, creating a fire sword using the broken piece as a conduit, due to its sacred properties. Kuwabara used the sword once more to fight the psychic Shorin (who later turned out to be the demon Rando). After the tournament, Kuwabara underwent rigorous training and learned to manifest a more powerful sword without the use of a conduit. From there he continued perfecting and creating new and stronger variations of the original technique.
Initially, Kuwabara channeled his energy through a broken piece of Musashi's sacred sword, expanding and manifesting the sword mostly by accident. After training himself to better use his spirit energy, Kuwabara manifested the sword by channeling his energy into a ball in the palm of his hand and squeezing it until it narrows and grows, taking the form of a sword.
The Spirit Sword looks somewhat like an English broadsword composed entirely of spirit energy that possesses a sunfire hue. However, outside a few promotional images, despite being called a 'sword' the Spirit Sword has rarely been show having any defined form, more like a slightly tapered oblong of energy. As such, the form does change throughout the series, sometimes taking on a much more narrow form resembling a katana.
Power and Effect
The Spirit Sword is extremely versatile, usable in both offense and defense. The power of the sword varies with Kuwabara's will: the more energy he puts to the sword, the sharper and sturdier it gets. Conversely, the sword is easily shattered if Kuwabara does not put enough energy into it. The first few times Kuwabara performed this technique, its effect was more akin to a bat than a sword: rather than cutting, it generated blunt force. If given a reasonable amount of energy, the blade is shown to be sharp enough to cut D Class and certain C Class demons in half. It has also been demonstrated to easily cut through rocks, trees, walls, metal and many other extremely durable materials. The Spirit Sword grew stronger alongside its user, but as the series's antagonists began to drastically eclipse Kuwabara in power, the sword's usefulness began to decrease accordingly. The sword can also be used for defense. Much like a bat, it can be used to counter projectile attacks, deflect attacks, or simply avoid direct collision. Although usually used in the size of a sword, the expansion allows Kuwabara to create derivative techniques such as Spirit Sword Javelin. In many ways, the Spirit Sword is really called a sword as a matter of convenience, as Kuwabara has repeatedly shown the ability to form the weapon into just about any shape he likes.
In the Chapter Black Saga, when Kuwabara faced Shinobu Sensui, the S class ex-Spirit Detective commented to himself that the Spirit Sword could barely slice through anything. He then proceeded to deflect the weapon bare-handed. It should be noted however, that Kuwabara was nowhere even close to as powerful as Sensui when he attempted to cut the former Spirit Detective, and that as such the technique's lack of effectiveness may have been due to the difference in power between the two combatants, just as is the case with most techniques.
Once Kuwabara was able to create his Dimension Sword, his normal Spirit Sword technique became somewhat obsolete due to the fact that the Dimension Sword can, simply by its nature, cut through anything. However, the Dimension Sword has nowhere near as many applications as it's more mundane sister technique.
- Double Spirit Sword (霊剣二刀流, Rei Ken Nitōryū, translates as Spirit Sword Two Blade Style; Double Aura Sword in the Viz translation): During his training before the Dark Tournament competition under Kurama and Hiei, Kuwabara develops the ability to materialize two swords at once, one for each hand. In the anime it is used only once, when he was fighting Rinku. In the manga, it was used twice, the first time being the battle against the demons on the boat to the Dark Tournament. This occurrence suggests the technique was developed by Kuwabara to augment his ability to defend against simultaneous attacks from multiple directions as well as to increase his offensive capability.
- Spiritual Strike: Kuwabara extends his Spirit Sword and uses his advanced Spirit Awareness to manipulate the weapon's flexibility so that it exhibits a type of tracking feature in order to hit its target. He first uses this attack on Rinku during the Dark Tournament.
- Spirit Sword Shards (霊手裏剣, Rei Shuriken, translates as Spirit Throwing Knives): This is a technique where Kuwabara produces small bolts of energy from his hands, similar to shuriken, and shoots the smaller spirit blades at the opponent. This can be considered Kuwabara's analogue of the Spirit Shotgun, since it is a multiple projectile attack, and weaker than the Spirit Sword.
- During the Poltergeist Movie, Kuwabara uses an attack in which he summons all his Spirit Energy to form a giant sword resembling a large column of spirit energy which he then strikes his opponent with. This is similar to Yusuke's Spirit Gun Mega as it is all of his remaining spirit energy focused into one final attack, and leaves him drained of spirit energy, causing him to resort to his fists after using it.
- Energy Blade Storm is used in Yu Yu Hakusho: Tournament Tactics. It is a long ranged attack where Kuwabara fires multiple orange spirit blasts at his enemy. It may be another name for his Spirit Sword Shards or is based off of it.
- The Trial Sword (試しの剣, Tameshi No Ken, translates as Sword of Trials; The Trial Sword in the English Dub): While preparing for the finals of the Dark Tournament competitition, Suzuki gives him the sword handle that Shishiwakamaru used; though, Suzuki explains, it will absorb Kuwabara's energy and turn into a form unique to him. With some practice, he is able to create a massive prismatic blade, of pure Spirit Energy, which also generates a unique, almost-electrical, aura that crackles around his entire body and improve both his offense and defense.
- Kuwabara is also able to make the blade change shape as well, turning it into what he calls the Spirit Flyswatter (巨大霊気棒, Kyodai Reikibō, translated as Giant Spirit Energy Staff), which he used to pummel and defeat Elder Toguro, who could not be killed because he could shift his vital organs around his body, in the final round of the Dark Tournament. Unnamed in the Viz Manga.
- Main Article: Dimension Sword