Age: (Not including the 50 years pinned to a tree) Unknown, but Takahashi says that his mindset is that of a 16 or 17 year old
Race: Half Dog Demon and Half Human
Weapon(s): Tessaiga (or known as Tetsusaiga), Sankon Tetsusou (soul scattering iron claw), Hijin Ketsusou (flying blade blood claws).
Loves: Kagome and Kikyo
Hates: Naraku, Sesshoumaru, and other bad guys
Personality: Quick tempered, uses rude language, arrogant but very thoughtful and emotional (although he seldom shows it to others). He has many inner conflicts, one of them is feeling responsible for Kikyou's death. He also doesn't quite know how to express his feelings for Kagome.
Weaknesses: Because of his half demon, half human blood, he becomes fully human every new moon. He loses all of his demon characteristics (his hair turns black, his eyes get dark, his nose and ears are human, and he has no fangs or claws), but more importantly, he loses his super-human strength and capabilities, and can no longer get Tetsusaiga to transform. When morning comes, he changes back.
Extra info: Inuyasha is a half demon, half dog demon to be percise. He fell in love with Kikyo, which later fell into death of Kikyo. Naraku turned them against eachother, and before Kikyo died she used a purification arow to hold Inuyasha on a tree for 50 years. After 50 years, Kagome came and took the arow out of him, and he awoke. Now, since the Sacred Jewl has been shattered and Inuyasha, Kagome, and a lot of other people/demons have joined them in the search for the shards.
EVEN MORE INFO
Growing up, Inuyasha had a difficult childhood. Being half human and half demon, he was ostracized from both worlds, never finding a place to fit in as a child. His father, a great dog demon lord, died when Inuyasha was born while his mother passed away early in his childhood. Although he has a half-brother, the full demon Sesshomaru, the two had a bad relationship due to Sesshomaru's distaste for Inuyasha's mixed heritage.
The rest of his early life was lonesome and isolated until he met the priestess Kikyo. Although they should have been enemies, the two slowly fell in love until the tragic day that Naraku pitted them against one another. Believing Inuyasha had betrayed her, Kikyo sealed Inuyasha to a tree with a magical arrow. Kikyo died, and Inuyasha slept undisturbed for fifty years until Kagome arrived and set him free.
Initially Inuyasha could not stand Kagome, due to her strong resembalance to Kikyo. To counter this, the magical Beads of Subjugation were placed around Inuyasha neck, forcing him to the ground whenever Kagome shouts "Sit!" The pair slowly grow close as Inuyasha journeys to find the scattered pieces of the Shikon Jewel, but when Kikyo returns to life Inuyasha begins to doubt his feelings for Kagome.
Due to his mixed parentage, Inuyasha also has to contend with an unusual affliction. Each month during the new moon Inuyasha looses his powers and turns into a human. This is when he is most vulnerable, and only his closest companions are aware of the time of his transformation. Another concern is when his demonic blood overtakes him, causing him to transform into a full demon. During this state Inuyasha is uncontrollable to such an extent that he attacks friend and foe alike.
Over the course of Inuyasha's travels he learns that it was Naraku who engineered his feud with Kikyo. With his sword Tetsusaiga in hand, Inuyasha's mission has gone beyond merely collecting the jewel shards, but getting revenge against Naraku for his evil acts. Initially Inuyasha wanted to use the completed Shikon Jewel to become a full-blooded demon, but he now has reservations for what that decision may bring.