Kōga

Koga (鋼牙 Kōga) is the young leader of the eastern yōkai-wolf tribe, 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 Koga 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, Koga 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, Koga 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).

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: " He has a name, Inuyasha! Stop calling him Mutt-face!" Koga threatens to kill him once he see's 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. At the end of the series Koga marries Ayame not knowing that Kagome had returned and married Inuyasha.

Koga's Appearance
He wears brown wolf fur skirt. 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. Koga has a brown wolf fur head band, black hair, and he wears silver and black armor. Koga 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.

Aliases

 * Chief (by some of his comrades)
 * Idiot/baka (by Inuyasha and once by Hakkaku)
 * Moron (by Inuyasha)
 * Wolf/Wolf Boy (by Inuyasha and Bankotsu once)
 * Mangy Wolf (by Inuyasha)
 * Bastard (by Inuyasha once)
 * Scrawny Wolf (main nickname by Inuyasha)
 * Freak (by Inuyasha)
 * The Man Who Fell In Love With Kagome
 * Wimpy or Pathetic Wolf (by Inuyasha)

Name Meaning

 * The 鋼牙 means "steel fang".

Abilities

 * Whirlwind - Koga's method of transportation. Whenever on the go, he is enveloped in a high-speed tornado. Despite its effectiveness, Koga never actually uses it in battle. He usually outruns Ginta and Hakkaku just to be held back.
 * Strength - In his battle with the Wolf Guardian, Koga 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 Koga 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 Koga.
 * Jewel Enhanced Abilities- Koga 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.
 * Stamina- Being a full-fledged demon Koga 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 Koga 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 Koga in the legs and drags him in his body. Naraku's miasma that could melt forests and mountains failed to melt or even severly injure Koga.

Triva

 * Koga did not appear in the movies.