Renkotsu

was a killer who was also a member of the Band of Seven. An expert military engineer, he creates explosives and incendiary devices, including a type of flaming oil that he can spew from his mouth, and reconstructs Ginkotsu into a living artillery weapon that resembles a modern tank. He is also a gifted strategist and has some skill at hand to hand combat, although the only members of the group he surpasses in fighting skills are Mukotsu and Kyōkotsu. One of the most dangerous members of the Band of Seven, he is also second in command after Bankotsu because of his intelligence.

During the story
Renkotsu first appears in the anime taking over a Buddhist temple; however, his scene is omitted from the manga. He then takes Inuyasha and his poisoned friends in after his battle with Ginkotsu and gains his trust. Later, after Ginkotsu attacks Inuyasha at the temple, Renkotsu sets the temple with Inuyasha's friends in it on fire, but not before stealing Kagome's Shikon Jewel Shards. He is spared by Inuyasha, and he and Ginkotsu regroup with the Band of Seven.

He reworks Ginkotsu into a tank, and then along with Jakotsu and Ginkotsu, collects Suikotsu. When reunited with Bankotsu, he is forced to give up the shards he stole from Kagome. Bankotsu promptly threatens Renkotsu with death if he keeps more shards for himself. Renkotsu appears later with Ginkotsu, fighting Kōga. They gain the upper hand at first, but Kōga causes Renkotsu to fall from Ginkotsu's back after critically injuring him. Ginkotsu, angered, unleashes all of his artillery upon Kōga. Kōga defeats him, but Ginkotsu self-destructs and uses his Shikon shard to protect Renkotsu (in the manga, Kōga stuffs Renkotsu's armor into Ginkotsu's cannon, causing it to explode). Renkotsu uses Ginkotsu's shard to heal his wound, despite knowing Bankotsu will kill him for doing so; his justification for this is that he will do anything to survive. Because Bankotsu's orders continue to send various members of the Band of Seven to their eventual deaths while returning their jewel shards to Bankotsu, Renkotsu uses this to justify his plan to betray Bankotsu.

He then attacks again by trapping Inuyasha, Kagome, Kōga, and Kōga's followers into a cave. He defeats Inuyasha and prepares to cut out Kōga's jewel shards, but is then handily defeated by Inuyasha's timely appearance. Later, after Inuyasha enters the barrier surrounding the Band of Seven's fortress and becomes human, Renkotsu chases him and toys with the helpless Inuyasha. Inuyasha slips through a crevice just as Jakotsu arrives; knowing Jakotsu has an obsession for killing Inuyasha, Renkotsu sends him after the half-demon, hoping the two will destroy each other. His reason for this is that Jakotsu is too loyal to Bankotsu to join his betrayal, and he needs Jakotsu's shard. Renkotsu observes the battle and removes Jakotsu's jewel shard after he was defeated by Inuyasha, apologizing to Jakotsu. With three jewel shards, he challenges Bankotsu, but dies after Bankotsu, deeming him a traitor, cuts all of the jewel shards out of Renkotsu's body.

Renkotsu's death happens slightly differently in the anime. When he finds Bankotsu, Bankotsu has already been told by the Saimyosho of his betrayal of Jakotsu. Renkotsu thinks that if he can keep Bankotsu from using Banryu, despite Bankotsu having one more shard they should be evenly matched- but then Bankotsu reaches up and yanks out Renkotsu's stolen shards, revealing his treachery. Infuriated, Renkotsu berates Bankotsu for sending the Band to their deaths once again, and states the only reason Bankotsu can overpower him is because of their shikon shards. Insulted, Bankotsu returns the shards to Renkotsu and challenges him to prove it by fighting him, laying Banryu aside. Suddenly unnerved despite having the shards, Renkotsu hesitates, and Bakotsu attacks. It is immediately clear that Renkotsu's combat skills are completely inferior to Bankotsu's; panicking, he unleashes his artillery and then his flame gourd, but it barely holds Bankotsu back. Bankotsu throws Jakotsu's hairpin and hits Renkotsu in the chest, paralyzing him and knocking out one of the jewel shards. Angrily, Renkotsu screams at him, "How is what I've done any different from what you've done?!" Bankotsu rips out his other shards in response; as Renkotsu crumbles into a skeleton, he answers, "The difference is... I would never betray my friends." meaning he killed Renkotsu to avenge Jakotsu.

Physical description
Renkotsu is bald, which is thought to be because it's said he was once a monk/priest (he is able to write). He has tattoos upon his face which stand for Deception. He usually wears armor and a bandanna. His original armor consisted of a blue undershirt with a reddish-orange armor, but after his battle with Kōga, in which much of his armor was torn off, Renkotsu adopts a new outfit with a black undershirt and orange armor with a flame-like design.

Powers & Abilities
Although not a formidable fighter like Bankotsu, Jakotsu or Suikotsu, Renkotsu makes up for his lack of combat skills with his advance weaponry. He is a master of chemistry, explosives, metallurgy & mechanics. He uses a variety of fire-based weapons, including "steel" strings that light on fire, cannons, and dynamite. He can also breathe fire by drinking a special oil and spitting it from his mouth (no explanation is given as to how the oil is lit, as it comes from his mouth as fire). He also has a wooden wheelbarrow that he uses to carry his artillery after Ginkotsu's death. It is his invention and engineering skills that allow him to rebuild Ginkotsu after his original body was damaged beyond repair.

Arguably the most cunning and intelligent member of the Band, Renkotsu is skilled in stealth and strategy; he is usually in command if Bankotsu is engaged in other matters, and unlike the others he rightly mistrusted Naraku (although the two never met face-to-face). He is also the only member of the Band besides Bankotsu who knows how to write. Ultimately, Renkotsu's cunning was his downfall, as it caused him to betray Bankotsu for his own survival. Bankotsu admitted that Renkotsu might have been able to usurp him if he hadn't hesitated so often to figure out the details of his plan, remarking, "For being the smart one, you sure can be stupid."

Weapons

 * Fire Gourd: Renkotsu has a gourd attached to his wrist which has an extremely flammable liquid inside of it, which he drinks then spits out as flames. This is his most commonly used, and simplest, weapon.
 * Fire Wire: Renkotsu has wires which he wields with his fingers. He can set them on fire instantaneously & use them to bind his opponents.
 * Fire Net: With his fingers interlaced, Renkotsu can make the wires form a net to keep the target from escaping by leaping/flying.
 * Fire Whip: Basically Renkotsu only using one Fire Wire & using it similarly to a whip.
 * River of Flames: Not really so much of a technique as a strategy. The idea of this strategy was to catch Kagome and Kōga at the foot of the mountain of the spirits, is to throw oil on the river(after making a dam from rocks dislodges by explosives) and then set fire to it, forming a layer of fire on the river.  Renkotsu's backpack contains canisters of oil and lighting devices for this purpose.
 * Flamethrower: A pump like device that launches a whirlwind of fire from it by pushing a pump in the back.
 * Bazooka/Cannon: A weapon of Renkotsu's that fires explosive rounds by pressing switch/button.
 * Gatling Gun: Another of Renkotsu's weapons, that can fire light explosive rounds in quick succession.
 * Explosives: He uses various types of explosives such as bombs, dynamite, etc. which are carried in his backpack.
 * Knife: Renkotsu is, besides Mukotsu, the only member of the Band of Seven who never displays hand-to-hand combat skills. However, he is shown to carry a long knife in his belt, which he intended to use to remove Kōga's shards. This, his agility and the fact that he killed all the monks in the temple without his firepower suggests he has at least basic knowledge of hand-to-hand combat.
 * Sensor: He uses a small sensor that he uses to put certain people to sleep. It works at a rather fast speed, knocking out both Kagome & Shippō in seconds.

Trivia

 * The tattoos on his face mean Deception, referring to him often using trickery to get what he wants.
 * Renkotsu's Theme-Music from the InuYasha Official Soundtrack, Vol. 3 is entitled "The Evil Renkotsu".