Goro Watari is a young college student who discovers he possesses powerful mutant abilities. His past is marked by sorrow, having lost his mother during his childhood and experiencing the painful separation from a childhood girlfriend named Teresa, who was taken away by an American soldier during the post-war occupation of Japan. Hailing from the Japanese island of Kyūshū, his fighting spirit is often expressed with the distinctive kiai cry of "Chest!"

As a hero, Goro is defined by a strong moral compass and a friendly, upright personality, combined with a cunning and strategic mind that allows him to outwit his opponents. He is also characterized by a profound compassion for children, always acting quickly to rescue any youngster in danger. This protective instinct is the driving force behind his motivation to fight, as he uses his powers to defend humanity from the numerous threats that emerge.

His unique transformation sequence involves two distinct stages. By crossing his arms and chanting "Gōriki Shōrai," he first transforms into Sanagiman, an armored, brown, larva-like creature. In this form, he has the ability to absorb the kinetic energy from enemy attacks, which charges a biomechanical power meter on his belt. Once sufficient energy is gathered, he crosses his fists again and shouts "Chōriki Shōrai," causing the Sanagiman shell to explosively shatter and reveal his true hero form, Inazuman. In his Inazuman Flash iteration, which appears in the sequel series, he gains the enhanced ability to hurl powerful lightning bolts at his enemies.

In his role within the story, Goro is initially a member of the Youth League, a group of similarly psychic-powered young people who battle evil. He shares a unique telepathic bond with Raijingo, a sentient flying car shaped like a shark that can fire missiles and physically attack enemies. Following the defeat of the Neo-Human Empire, Goro faces the darker and more dangerous Despar Army in Inazuman Flash. During this conflict, his primary ally becomes Makoto Arai, a cynical Interpol agent who is later revealed to be a cyborg. While his friends from the Youth League largely vanish from the narrative, his partnership with Makoto becomes central to his fight.

Throughout the series, Goro demonstrates significant development. He transitions from a college student who has his powers awakened to a seasoned warrior who faces ever-evolving enemies. This is marked by his progression from the original Inazuman to the more powerful Inazuman Flash, reflecting his adaptation to greater threats. His notable abilities are extensive and include superhuman strength and speed, the power of flight, teleportation, and the use of his yellow scarf, which he can morph into various weapons such as a whip-like chain. His signature finishing move is the Supreme Lightning Strike, a devastating electric attack used to destroy his foes. He also possesses a restorative ability known as the Reverse Chest, which can undo the damage caused by his enemies.