Inuyasha may look young but he is in fact 200 years old, he is also half-brother to Sesshomaru who despiess him for killing their father who died to protect the infant Inuyasha and Izayoi from Setsuna no Takemaru.
Inuyasha would wreck havoc upon a village that held the Shikon Jewel but at every attempt, he was stopped by Kikyo, a priestess residing in the village, he originally wanted the Jewel to become a full demon but by spending time with Kikyo, he fallen for her and wished to become human, however, that was not mean to be as Onigumo who became Naraku, deceived them both and the end result, he was pinned to a tree for 50 years in suspended animation as Kikyo died from her wounds.
50 year later, Kikyo's reincarnation, Kagome Higuarashi would break the seal to be saved from a Centipede Demon, Inuyasha would save her and demanded the SHikon Jewel, however, Kaede, Kikyou's sister placed a charm upon him in form of beads that would react to the word Sit by Kagome, halting Inuyasha completely.
Kagome however, would shatter the SHikon jewel by accident with her arrow to kill a Crow Demon and the Jewel shattered, scattering Jewel Shards across the land and to that end, Inuyasha had to team up with kagome who could sense the Jewel Shards but he and Kagome would soon be joined by Shippo, a child fox-demon, Miroku, a peverted monk with a cursed hand that devours all it's path and Sango, a demon-slayer whose village was exterminated by Naraku.
Inuyasha however, has one weakness, the Night of the New Moon where his demon powers dimish greatly that he's a full-fledged human, the changes are very noticble, his hair would be pure black with no gold eyes and hsi nails retracted with his enchaned senses reduced greatly as well as his strength, he keeps this weakness to hismelf and eventually to his companions so their enemies won't use it to their advantage.
Inuyasha is also the wielder of oen of the Swords of Conquest, the Sword of Man, Tetsusaiga that slay 100 enemies in one sweep, this sword originally belonged to his father which was created from one of his fangs and eventually, Inuyasha's own after it was broken, it cannot transform however when he's human but it has a barrier to prevent full blooded demons from using it, even Sesshomaru desires it as he was left with Tenseiga, the Sword of Heaven that can save 100 lives in one sweep.
Inuyasha may coem off as rude and tought but underneath that exterior, he cares for others and would protect them with his life if he had to, he is torn apart by his old love Kikyo who is revived as ash and bones and Kagome, the reincarnation of Kikyo, however, in the end, he chose Kagome and eventually defeats Naraku and marries her after three years from being seperated from her.
Inuyasha too joined the battle at Sky City, protecting Harry Potter, Ron Weasely and Heromine Granger from harm and seems to see Ichigo Kurosaki as a comrade along with others, he is able to see the demonic power or soemthign similar to it emitting from ichigo's black getsuga and combines it with the Backlash Wave.
Inuyasha was also present at the battle of Unbreakable Dark with Tetsusaiga infused with the special magic that damages her and attacked her with the Wind Scar and Adamant Barrage respectively.