Author Rumiko Takahashi once stated in an interview that Inuyasha is an akita inu. According to Ms. Takahashi's official Zusetsutaizen Ougikaiden character data book, Inuyasha's age in human years is unknown, but his appearance and general behavior are "equivalent" to a human fifteen-year-old at the start of the series. However, the movie canon suggests an actual age of 150 human years since the Sou'unga was sealed two hundred years prior to the feudal era period. Inuyasha was shown to be born at that time, and he was sealed away for fifty years, providing 200 - 50 = 150 years. This is consistant with European concepts of the Fay, Farie, Elvish, or Tuatha De Danaan (various spirits, sprites, daemons, etc) as aging far more slowly than humans, even to the point of appearing immortal.