Hayate (Japanese: 疾風) is a shinobi and the eighteenth master of the Mugen Tenshin clan. He is the eldest and only son of Shiden and Ayame, making him Kasumi's older brother, Ayane's older half-brother and cousin, and Honoka's cousin. He is also friends and allies with Ryu Hayabusa.
Although he was first mentioned in the first Dead or Alive in 1996, Hayate's official debut appearance was in the 1999 title Dead or Alive 2 as Ein; an amnesiac karateka. He regained his memory during the second game and finally appeared as himself in 2001 for Dead or Alive 3.
Hayate is the eldest child and only son of Shiden, the now-former leader of the Mugen Tenshin clan, and Ayame. He was born to be the next leader of the clan, to follow on from his father. He seemed to have a happy childhood, training in the art of the clan, Tenjinmon-styled ninjutsu, with his younger sister Kasumi, who loved him dearly.
After Genra requested to Shiden for Ayane - the village's "cursed child" and his foster daughter - to begin her training, Hayate started to form a friendship with the girl, treating her with kindness, which most of the clan didn't give her.
The two formed a strong bond, but soon after, Ayame admitted to Ayane that she was her daughter, meaning that she was a half-sister to Hayate and Kasumi. Despite this life-changing revelation, and the falling-out between Ayane and Kasumi, Hayate remained to have strong relationships with both of his sisters over the years.
During his early life, Hayate also became good friends with Ryu Hayabusa, who like him was next in line to be the master of his own clan, the Hayabusa clan.