Jundai Kayahara, often called by the nickname Kaya, is a supporting character in the anime Kuromukuro. He is a student at Tateyama International High School and a classmate of the main protagonist Yukina Shirahane. Jundai is notably short in stature with dark hair, light skin, and freckles, and he has brown eyes and brown hair that is cut to ear-length. His most defining physical trait is that he is almost never seen without a camera in his hand.

Jundai's personality is driven by a powerful obsession with social media and his online presence. He is always looking for the next exciting thing to film and livestream, with a primary goal of gaining more viewers for his broadcasts. This enthusiasm leads him to dive headfirst into situations that interest him, often without considering the potential risks to himself or others. His desire for dramatic footage can make him seem strange or reckless, but underneath this obsession, he is generally portrayed as friendly and possessing a positive, energetic outlook. His daring and sometimes crazy attitude is a trait he apparently inherited; it is revealed that his father is the eccentric Dr. Hausen, a scientist whose own single-minded dedication to research led to his divorce from Jundai's mother.

Within the story, Jundai fills a unique role among the group of high school students. While others become directly involved in piloting mecha or tactical operations, his primary function is as a documentarian. He frequently attempts to record and stream the extraordinary events unfolding around his friends, including the operations of the giant robot Kuromukuro. This desire for a scoop leads him to take considerable risks, such as trying to film inside a geoframe's cockpit and broadcasting the footage to the world. Despite his seemingly self-serving motivations, his actions do contribute to the narrative, and even his minor role is considered useful for the series development. A key relationship that provides background for his character is with his father, Dr. Hausen, from whom he attempts to secretly obtain video recording equipment.

While Jundai does not undergo a dramatic transformation, his consistent behavior serves as a foil to the more serious characters. His unwavering commitment to getting the perfect shot, even in the face of danger, adds a layer of chaotic energy to the group dynamic. In terms of notable abilities, Jundai possesses no combat or piloting skills. His primary talent lies in his ability to operate cameras and streaming equipment, using his technical know-how to capture and distribute live video from the heart of the conflict.