Tōkijin

was a great sword that was forged from the fangs of Goshinki, the third incarnation of Naraku, which was both commissioned to be forged and subsequently wielded by Sesshōmaru.

History
Sesshōmaru abandoned his quest to obtain Tessaiga, but instead searched for a sword that could rival it. He discovered the remains of Naraku's incarnation Goshinki, who was able to break Tessaiga with its own fangs. Sesshōmaru, having discovered this, decided that the fangs would produce a powerful sword that could rival the Tessaiga. He requested that the swordsmith, Kaijinbō (a former apprentice of Tōtōsai, but who was expelled for killing ten children and using their fat and blood to increase the power of one sword) to create a sword from Goshinki's fangs. At first, Kaijinbō refused because he could not create a great sword from a dead yōkai, but Sesshōmaru revived him with the Tenseiga, at which point Kaijinbō gladly accepted his request.

Upon the completion, Tōkijin possessed Kaijinbō and he killed Jaken who was checking on the sword's progress. Goshinki's hatred for Inuyasha was so great that the Tōkijin also bore the hatred, and Tōkijin forced Kaijinbō to go after Inuyasha. Kaijinbō was not strong enough to bare Tōkijin's great power, so when he battled Inuyasha who wielded Tessaiga, his body was destroyed by the pressure of the two blades. Sesshōmaru (who revived Jaken to discover what happened to the sword) found Tōkijin, claimed it, and dissipated the evil aura that possessed Kaijinbō. Sesshōmaru wanted to test the Tōkijin against Inuyasha and the Tessaiga and discovered the change in Inuyasha's blood. Tōkijin was able to match Tessaiga in power and gave Sesshōmaru the advantage in the battle (The reforged Tessaiga too heavy for Inuyasha to wield). The battle ended when Inuyasha transformed into a full yōkai and his friends escaped with him, while Tōtōsai distracted Sesshōmaru.

Signature Weapon
Tōkijin became Sesshōmaru's signature weapon after the battle. Over time, Sesshōmaru's mastery of the sword revealed its true power. Originally Tōkijin fired needle kenatsu that cut the enemy without the blade actually touching them. Tōkijin developed a stronger kenatsu that released a powerful blue energy wave made of yōki; the attack was similar to the Kaze no Kizu. In the InuYasha movie series, Sesshōmaru could channel a large amount of his yōki into the Tōkijin to release the Sōryūha which rivalled the Bakuryūha.

Because Tōkijin was forged from the fangs of an oni, it limited the amount of yōki that Sesshōmaru could release. After the Sōryūha was used, Tōkijin could not be used until it recharged. As Tessaiga and Tenseiga were forged from a daiyōkai's fangs, they did not have this limit.

Destruction and Replacement
When Sesshōmaru battled Mōryōmaru for a second time, he insulted Kagura in front of Sesshōmaru, which angered him. Sesshōmaru unleashed the most powerful yōki wave ever produced by Tōkijin which damaged Mōryōmaru's shoulder armor and shattered his arm. He pushed Tōkijin into Mōryōmaru's armor and cracked it, but the stress applied to Tōkijin broke the sword.

Sesshōmaru refused to get Tōkijin repaired because it did not have the power to defeat Mōryōmaru and instead found a replacement sword, which he eventually found when Tōtōsai reforged Tenseiga into a weapon with a new technique.

Physical description
Unlike most other weapons in the series, Tōkijin resembled a long hilt Indian Khanda (Basket hilted two-handed Khanda), a double-edged straight sword which is wider at tip and narrower at base, being the only sword with this type of blade in the world, inspired from the representation of Acalanath Vidyaraja or Fudo Myo o, the Buddhist fierce god of protection who wields the Vajra Khadga also known as Kongo-ken or Thunder-sword (see Wikipedia article Acala). It had a yellow cross guard, red hilt and yellow round pommel with a red thread tied to it.

Powers & Abilities

 * Aura: When wielded by Kaijinbō, the sword constantly emitted an intensely evil aura, so much that it ended up consuming its own creator, Kaijinbō, body and all. The aura itself was so sinister that other demons were unable to go even near it, until it was succumbed by Sesshōmaru. It was a pale reddish energy aura in color. The aura dissipated when Sesshōmaru touched it. Tōtōsai claimed that it lost to Sesshōmaru, while Sesshōmaru stated that the sword chose him as its master.
 * Kenatsu: This ability allowed Tōkijin to slash enemies with its yōki without direct contact. Initially, Tōkijin fired needles of kenatsu which could dispose of many yōkai, but Sesshōmaru later developed a stronger kenatsu, composed of a massive wave of blue yōki, similar to the Kaze no Kizu. Later, Sesshōmaru developed a second kenatsu that fired a massive sphere of green-blue energy.
 * Tōkijin's strongest and most powerful only named attack. When Sesshōmaru charged yōki into Tōkijin, and then released a massive amount of yōki in the form of light-blue glowing arcs of lightning. In the Fourth Movie, the Sōryūha became stronger and manifested in the form of a blue dragon that was composed of pure energy and lightning. The "Dragon Strike" was at first shown to be equal in power to the Bakuryūha, but when Sesshōmaru channeled his anger into Tōkijin to strengthen and enhance the attack even further, it eventually overpowered the Backlash Wave. It was only featured within the movies and the anime.
 * Energy Slash: There were times where yellow lightning was released from the blade. However, this ability was only demonstrated in the PS2 game, InuYasha: Feudal Combat.
 * Protective Barrier: When struck into the ground, Tōkijin can create barrier that would eradicate anything that comes into contact with it.