The manga focuses on a plot more similar to the anime starting with Koji checking on his grandfather after Baron Ashura had activated a bomb. With his dying breath, Dr. Kabuto gives Koji the Super Robot Mazinger Z. With the threat of Dr. Hell looming, Koji fights against his Mechanical Beasts and lieutenants with help from Sayaka Yumi and, to some degree, Boss.

(Source: Mazinger Wiki)