The original work, Grappler Baki, began back in 1991 and ran for 42 volumes through 1999 as done by Keisuki Itagaki.
He then kicked off the next series in the property in 1999 with Baki: The Search of Our Strongest Hero, which ran until 2005 with a total of 31 volumes released.
What we’re now learning is even more interesting as this iteration of the franchise from 1999, New Grappler Baki: In Search of Our Strongest Hero, is the one getting adapted as it works the Death Row Convicts arc.