Prof. Grey Bomber, also known as Dr. Graybon, is the grandfather of Blue Bomber. He invents and maintains the B-Da Armors used by the heroic Bombers—White Bomber, Blue Bomber, Red Bomber, and Yellow Bomber—to fight evil and protect B-Da City. These armors are developed and stored in his laboratory, assisted by his grandson and the B-Daron Rui-Rui.

Trained alongside Dr. Shadow in mechanics and technological science by his mentor, Professor Bomber (Dr. Master Bom), Prof. Grey Bomber possesses a lively, active demeanor and an optimistic outlook despite his age. He seeks recognition for his inventions and holds a high opinion of his abilities, justified by his technical contributions.

His backstory includes attempting to dissuade Dr. Shadow from turning evil, efforts which failed. His research data contained blueprints for advanced combined armors like the Saint Blaster, crucial in later conflicts.

During *Bakugaiden V*, he remains the primary developer of battle suits for the B-DaCops (Shirobon, Aobon, Kurobon, Akabon, Kiirobon, Midoribon), aided by the bat-like Mimitan. His work is central to combating antagonists like the Devilvader organization.

Prof. Grey Bomber faces a professional rivalry with Geniusbon, another scientist whose creations challenge the B-DaCops, adding pressure to his role as a technological innovator.

Earlier in the series, after Professor Bomber's death, a fragment of Prof. Grey Bomber's will was preserved in a computer system. This allowed him to communicate posthumously via hologram with White Bomber and allies during critical moments. In the final battle against overarching threats, he manifested alongside other deceased allies like Yurei Bomber and Icekenstein as a spirit to observe and support the heroes.