Hajime Hoshino is a character from the television series Kamen Rider Amazons. He is a former professor of Jin Takayama and the father of Iyu Hoshino. His background is deeply tied to the central conflict of the series, as he becomes one of the first so-called New Type Amazons, specifically known as the Vulture Amazon.

In terms of personality, before his transformation, Hajime is portrayed as a caring and compassionate individual. He is shown to value life, demonstrated by his reluctance to harm the unborn Chihiro, whom Jin intended to kill out of a sense of duty to protect humanity. His caring nature extends to his own family, as he is described as a loving father who takes great care of his daughters.

Hajime's motivations are rooted in his protective instincts. When Jin comes to him to discuss his wife Nanaha's pregnancy, Hajime perceives Jin's intention to kill the child. Driven by his own moral code, he decides to help Nanaha escape with the baby, Chihiro, after he is born. This act of defiance against his former student sets in motion tragic consequences for his own family.

His role in the story is that of a tragic figure and a cautionary example. He is a scientist who becomes a victim of the very phenomenon he studies. He cooperates with Haruka to better understand the nature of human-Amazon hybrids, particularly Chihiro. However, his research takes a horrifying personal turn when he discovers that the hybrid cells have entered his own bloodstream through a minor cut, transforming him into an Amazon without his knowledge.

Key relationships define his narrative. His bond with his daughter Iyu is central; his monstrous actions directly affect her. His professional and moral conflict with Jin Takayama serves as a catalyst for the plot, as his decision to save Chihiro creates an enduring rift. He also works with Haruka, who is seeking answers about his own nature, though this collaboration ends in tragedy.

Hajime's development is a tragic arc from humanity to monstrosity. The transformation triggers on his birthday while he is celebrating with his family. The Amazon urges completely overwhelm his consciousness, leading him to kill and eat his family members. In this feral state, he also attacks his daughter Iyu, nearly killing her and eating her left eyeball before being stopped.

Regarding notable abilities, as the Vulture Amazon, Hajime possesses the enhanced physical capabilities common to Amazons, including immense strength and a ravenous predatory instinct. His most significant, though tragic, ability is his involuntary and complete transformation into a New Type Amazon, which results in a total loss of human consciousness and a singular drive to feed on humans. His life ends when he is killed by Haruka, who transforms into Amazon Omega to stop his rampage.