Yasuhiro Nightow is the dude who created the characters and story for Gungrave. He is mostly known for his creation of Trigun. He was born on April 8, 1967. He wasn't always a manga artist. At first he was trying to get into social science and then he was sorta in real estate. Then he started working on doujinshi in college. He was still trying to sell houses and only later did it hit him, that he was into comics. His early works were Call XXXX (Super Jump) and Samurai Spirits(some game comic).
Some of Nightow's influences include Fujio Akatsuka, Atsuhiro Ohtomo, and Fumiko Takano. Aside from manga, his hobby is collecting action figures. He isn't really into video games.
Like most mangaka, Nightow spends most of his time drawing, eats and sleeps in between, and his vacations aren't enough for him. Speaking of eat, his favorite food is Nori. Some seaweed thing that you wrap sushi in.
As for his religion, he is Catholic. While that is so, he still has traces of Buddhist-like mannerisms in him.
There you have it. The dude that made Gungrave possible.
Reference from this Interview.