Kōga

was the young leader of the eastern yōkai-wolf tribe, or the Yoro clan, which is nearly wiped out by Kagura and Naraku. He first meets Inuyasha as an opponent in battle, but becomes a reluctant, occasional ally despite maintaining a strong sense of rivalry with the "useless mutt" about their relative combat strengths as well as Koga's persistent courtship of Kagome.

Although Kōga often flirts with Kagome, it is later revealed that he has promised Ayame, another wolf demon, to make her his wife. Later in the episode, Kōga tries to get Ayame to leave by saying he will only marry someone who can see the Sacred Jewel Shards. At the end of the anime it is revealed he did in fact marry Ayame. This does not happen in the manga because Ayame is a filler character.

After suffering serious wounds, Kōga is partially restored by three Shikon shards embedded into his legs and right arm. The shards are eventually taken away from him by Naraku, gravely weakening him; he leaves and disappears from the manga, after telling Kagome that she may leave Inuyasha and come to him at any time. In the anime the epilogue reveals that he married Ayame and has become the new chief of the wolf demon tribe (again, he only marries Ayame and becomes chief of her tribe in the anime).

History
Prior to his meeting Kagome and her friends, not much is known about his past or his parents. It seems that he is the youngest leader of the wolf-demon tribe thus far and he once promised a much-younger Ayame to take her as his wife. This occured during a lunar rainbow, though he later denies that this incident ever occured. It also seems that he has a solid, possibly long friendship with Ginta and Hakkakku.

During the Story
Kōga kills a wolf demon who betrayed him when he came for a hut that belonged to Rin (who later becomes Sesshomaru's companion)

Relationships
* Kagome

Koga first appears in episode 36: "Kagome Kidnapped by Koga, the wolf demon!" when he kidnaps Kagome and Shippo only because Kagome can see the sacred jewel shards in the Birds of Paradise, at first. Later in the next episode, Koga claims Kagome to be his "woman," receiving a slap from Kagome. When Kagome says: " His name isn't InuTrasha, so don't insult him! He's brave, courageous, really good-hearted when he's not being a jerk, and he's got a great name so say it right. Inuyasha." Koga threatens to kill him once he sees Inuyasha again. During the series, Koga saves Kagome multiple times while Inuyasha attacks the demon/enemy. Inuyasha tends to get jealous when Kagome is kind to Koga before chasing him off. Kagome thinks of Koga as a friend.


 * Ayame

Koga first met Ayame as a young girl after he saved her from a demon. Ayame is the grand-daughter of the chief in the northern mountains. Koga promised to marry her when she was younger, so Ayame comes searching for Koga in order to return to the northern mountains and restore balance among the tribes. After Koga refuses to go with Ayame, she returns back to the mountains alone, and sometime later the two meet each other. In the end of the anime series only, Koga marries Ayame not knowing that Kagome had returned and married Inuyasha.


 * Inuyasha 

Inuyasha was seen by Koga as a love rival for Kagome. They each have a name they call each other- Inuyasha is Mutt-Boy and Koga is Wolf-Boy. Although later they do become allies, Inuysha seems to be the winner of their rivalry since he marries Kagome.


 * Sesshomaru 

Koga met Inuyasha's half-brother in episode 99. Sesshomaru's companion, Rin, was killed by Koga's wolf pack before Sesshomaru brought her back to life with his sword. In the episode Koga meets Sesshomaru and they seem to be off to a horrible start when Koga talks about Inuyasha (being a half demon)however during the meeting Rin is attacked by a centipede like demon that Koga kills. They seemed to have a mutual understanding and still it seemed like this confrontation would have turned into a fight if Koga hadn't have saved Rin.

Physical appearance
Kōga has blue eyes and black hair that is always tied up into a ponytail with a brown cord. He wears a brown wolf pelt. He has a tail that is like a bushy wolf's tail, which is the same shade of brown, though it is in fact part of his body. Kōga has a brown wolf fur head band, black hair, and he wears silver and black armor. Kōga also has brown wolf fur as shoulder plates. He carries around a sword, entirely for decoration, however he does use it once as a last resort. His ears are pointed and resemble those of Sesshomaru and other demons. He is also usually seen with his posse of wolves and wolf demons, namely Ginta and Hakkaku

Abilities

 * Whirlwind - Kōga's method of transportation. Whenever on the go, he is enveloped in a high-speed tornado. Despite its effectiveness, Kōga never actually uses it in battle. He usually outruns Ginta and Hakkaku due to his impatience.
 * Strength - In his battle with the Wolf Guardian, Kōga could easily lift the body of the Goraishi Guardian and throw it. Also he has proven to scuffle with Inuyasha, who is very strong, in mere fist fights. In The Final Act, he was also able to hold Inuyasha's Tessaiga with little effort despite being greatly hurt.
 * Goraishi - A claw that Kōga earns from his ancestor spirits so that he can avenge the deaths of his comrades and destroy Naraku. It creates energy blasts that are equal to that of a fully-powered Wind Scar. The claw shields him, barely, from Naraku's corruption of the jewel but it was only able to protect him once. The Goraishi has literally become a part of Kōga.
 * Sword- Kōga has a long sword at his hip, but he has never used it.This is because his Wolf-Demon clan instincts do not rely on weapons. However this is does not apply to the Goraishi because it has literally become part of Kōga body.
 * Jewel Enhanced Abilities- Kōga originally possessed three jewel shards: one in each leg and one in his right arm. These allowed him to run at exceptional speeds and increased the strength of his right arm. He eventually lost all three shards throughout the series, losing the 1st one from his arm at the end of episode 37.
 * Stamina- Being a full-fledged demon Kōga has incredible stamina. He states that he can run three days without stop and he can fight for a long time even when he is wounded.
 * Endurance- Being a demon Kōga has enhanced endurance. Even when he is seriously wounded he can still fight. In the battle with Ginkotsu and Renkotsu he defeated them even though his legs were badly injured. Another proof of his endurance is then Naraku impales Kōga in the legs and drags him into his own body. While trapped within Naraku, his miasma that could melt forests and mountains failed to melt or even severly injure Kōga.

Trivia

 * Kōga is the only one of the 10 Main characters to not appear in any of the movies.
 * Kōga constantly tried to woo Kagome, but to no avail.
 * It was Kōga's wolves that killed Rin.
 * In the Holy Pearl both You Ming and Rou Di based of Kōga and Miroku
 * Kōga is similar in appearance to to Ryoga Hibiki from Ranma 1/2, who is also romantically interested in the female protagonist and has a similar name that in part means "fang".