Hayate is a character the Dead or Alive series, as well as the brother of Kasumi and half-brother of Ayane. After being captured, he was taken to Germany, but was left to die in the Black Forest.
During his ordeal, Hayate lost his memory, but retained his fighting skills. Hitomi rescues him from the forest, and after he recovers, he takes the name Ein and trains at a dojo run by Hitomi's father. He enters the second Dead or Alive tournament in order to find out about his past. He manages to succeed in this desire, and returns under his true name in later entries.