Hayate is one of the major character of the Dead or Alive video game series. He is a shinobi and the eighteenth master of the Mugen Tenshin Ninja Clan. He is the oldest child and only son of Shiden and Ayame, making him Kasumi's older brother and Ayane's older half-brother and he is good friends with Ryu Hayabusa.
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 being used as a test subject by the Dead or Alive Tournament Executive Committee for Project Epsilon, Ein was left to die in the esoteric Black Forest of Germany. Even though he suffered amnesia, his deep desire to fight stayed within him. Soon afterwards, he mastered Karate in a very short period of time. He seeks answers about his past through participating in the "Dead or Alive 2 World Combat Championship."
After his appearance in Dead or Alive 2, Ein was replaced by both his true identity, Hayate, and Hitomi, a friend of Ein who shares the same martial arts style of Karate. Despite Hayate being "Ein" only for a short period of time, "Ein" has appeared as a recurring unlockable character in a variety of DOA titles following his first appearance.
After a battle with his sister, Kasumi, Hayato finally remembers his past. He is Hayate, ninja of the wind. Hayate is the 18th leader of the "Mugen Tenshin" style. He eventually learned that he was the subject of DOATEC's experimental superhuman project (Project Epsilon), which caused his memory loss. After recovering his memory, he was officially ordained as leader of the Mugen Tenshin style. Shiden is Hayate's father and Raidou is his uncle.
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.
Hayate has a strong sense of duty when it comes to his role as a leader, and as a shinobi of his clan. He is so devoted to the clan's rules and traditions that he would even hunt down his own runaway sister, albeit with much reluctance.
Although he could easily kill an enemy, Hayate is an honorable, caring soul when it comes to his family, friends, and allies. Hayate was close with both of his sisters, and despite the girls' rivalry between each other, he has tried to remain friends with them. Even after Kasumi ran away, Hayate could never bring himself to strike her down or commit to her death. He has also shown that he is a very protective older brother; when Brad Wong tried to hit on Ayane, Hayate was quick to use brute force to get the man away from her.
Hayate has also shown to have a competitive nature, with his friendly rivalry between his friend Hayabusa. While very serious when it comes to important matters, he isn't above having a bit of fun from time to time.