As Goro Watari and his friend Gosaku Marume are walking home from college classes one evening, they discover two children being attacked by evil mutants. After saving the kids, Watari discovers that the kids are part of the Youth League and were attacked by soldiers from the Neo-Human Empire. After being taken in by the Youth League, it is discovered Goro is a very powerful mutant and, after having his powers awakened by the Youth League, Goro becomes able to transform into Sanagiman. Not only that, when "Sanagiman matures, his belt reaches maximum and he becomes Inazuman!"
With his new powers, which include the ability to teleport, turn his scarf into a giant chain, and the "Supreme Lightning Strike that finishes off his opponents, Inazuman battles Emperor Bamba, the head of the Neo-Human Empire, and his hoard of monsters.
The first television series ran from October 2, 1973 to March 26, 1974 with a total of 25 episodes, concluding with a two-part finale that led into the beginning of the sequel series, Inazuman Flash (イナズマンフラッシュ, Inazuman Furasshu), which aired in 1974 from April 9 to September 24 with a total of 23 episodes.
A manga adaptation by Shotaro Ishinomori was also serialized from 1973 to 1974.
Inazuman would later receive a tribute in the Kamen Rider Movie War film Kamen Rider × Kamen Rider Wizard & Fourze: Movie War Ultimatum, which features a rebooted origin for Inazuman.
This show provides examples of:
- Adaptational Expansion: The manga expands on several characters and concepts introduced in the series. The Youth League play a much more prominent role in the plot, with their leader Captain Sarra being a recurring character as opposed to disappearing immediately like he did in the Toku, and Inazuman's mother, who only appeared for a single episode in the show, is given an extended arc and much more development.
- Armies Are Evil: The two factions Inazuman fights are the Phantom Army and Despar Army. The Youth League by contrast has much less of a militaristic vibe to them and acts as more as support to Inazuman.
- Bare-Fisted Monk: Like the other Toku heroes of his time, Inazuman's main weapon (besides his electric abilities) is his fists.
- Big Bad: Emperor Banba, the leader of the Neo-Human Empire. Followed by Führer Geisel, the leader of the Despar Army.
- Bittersweet Ending: The first show ends with the Neo-Human Empire finally defeated, but the Despar Army still at large.
- By the Power of Grayskull!: To become Sanagiman, "Gouriki Shōrai"note , To change into Inazuman, "Chōriki Shōrai" note .
- Chuck Cunningham Syndrome:
- The leader of the Youth League, Captain Sarra, has very few appearances after the first episode.
- Gosaku, Satoko, Katsumi and Kaoru all vanish from the plot in between Inazuman and Inazuman Flash'', as Goro leaves to fight the Despar Army on his own and has Makoto Arai as his only recurring ally.
- Comic-Book Adaptation: A manga adaptation by creator Shotaro Ishinomori was serialized in Shogakukan's Weekly Shōnen Sunday from 1973 to 1974.
- Cool Car: Goro has Raijingo, which can fly and shoot anti-air missiles.
- Cue the Sun: Flash ends with Goro and Makoto standing with Makoto's wife Chizuko and their daughter Rumi, who has never seen the real sun on account of growing up inside Despar City, all watching the sun rise.
- Dem Bones: The Monster of the Week in episode 4 is the skeletal Bone Banbara.
- Dimension Lord: Several Mutant Robots appear to control their own pocket worlds themed after their specific gimmick, which they can pull Inazuman into.
- Early-Bird Cameo: The final two episodes see Udespar and Fuhrer Geisel making their debut, before going on to be the villains of the sequel series.
- Enemy Civil War: The anti-mutant sensibilities within the Neo-Human Empire eventually form the Despar Army to rebel against Banba for trying to ally with mutants.
- Enemy Mine: Goro and Banba briefly ally in the finale when the Despar Army threatens them both. It doesn't last, and Banba ends up double-crossing Goro to try to kill him one last time.
- Friend to All Children: Inazuman is always quick to help any children in trouble.
- From Dress to Dressing: In episode 17, Goro tears off his shirt sleeve to treat a child who was wounded. It becomes a plot point later on when the torn sleeve is later used to identify the real Goro against his impostor.
- Gas Mask Mooks: Both the Mooks of the Phantom Army and Despar Army wear gas masks.
- Henshin Hero: Unique in that Inazuman has two "Henshins" he must do before he assumes his titular form.
- Kiai: As both Sanagiman and Inazuman, his kiai fighting cry is "Chest!", which originates from the Japanese island of Kyūshū where the main character, Goro Watari, hails.
- Legion of Doom: In the Non-Serial Movie, Goro has to go up against a group of 14 Mutant Robots he faced in the past.
- Make Way for the New Villains: The Despar Army usurp Emperor Banba as ruler of the Neo-Human Empire in the finale of the original series, before becoming the villains of the sequel show.
- Mêlée à Trois: The finale of the original Inazuman features a three-way battle between Inazuman, Emperor Banba and the newly emerged Despar Army.
- Mid-Season Upgrade: Mid-show upgrade more like, but Inazuman gains his new Flash form at the end of the original series, which he uses throughout Inazuman Flash.
- Missing Mom: Goro lost his mother as a child. It later turns out she is a member of the Neo-Human Empire.
- Monster Misogyny: The Mutant Robot in episode 18, Poison Banbara, only targets beautiful women to use its Hate Plague poison on.
- Monster of the Week: The Neo-Human Empire has their "Mutant Robots" while the Despar Army has the "Robot Fighters".
- Nebulous Evil Organization: The Phantom Army, the military wing of the Neo-Human Empire, which seeks to destroy humanity so the mutants can claim the Earth.
- New Season, New Name: As part of the Retool, the second season of Inazuman was marketed as "Inazuman Flash" to differentiate it from its predecessor.
- Non-Serial Movie: A 3D movie was made that serves as an alternate retelling of episodes 24 and 25 and was released before the series ended, in order to get people excited about Inazuman Flash.
- Out of Focus: The Youth League makes more sparing appearances as the series goes on, with Katsumi, Satoko and Kaoru being the only members who appear most of the time.
- Plucky Comic Relief: Gosaku, whose antics are the source of most of the comedy in the series.
- Psychic Powers: Mutants in this series are shown to possess inherent psionic abilities.
- Retool: Went through one midway through in an effort to pull in more viewers. Notable changes included the Youth League being phased out a third of the way through and a more serious storyline developing where Goro became more personally invested in his fight against the Neo-Humans. The final third also saw some changes being made to the shows format, including more emphasis being placed on the Monster of the Week and the last few episodes laying the groundwork for Inazuman Flash.
- Reforged into a Minion: Several Mutant Robots were originally mutants who, willingly or otherwise, were converted into monstrous Neo-Humans to boost their psionic powers.
- Underground City: It's revealed in the final episode that Despar City is this, existing underneath Japan and using an artificial sun to give the appearance of being above ground.
- Why Don't You Just Shoot Him?: There are several times where the Neo-Humans have an opportunity to finish Goro off, but don't. Episodes 16 and 21 see Goro getting incapacitated due to poison, but the Neo-Humans choosing to wait for him to die from it instead of doing anything to speed up the process.
- World-Healing Wave: Inazuman's "Reverse Chest", which is capable of undoing any damage caused by the Mutant Creatures.
- Would Hurt a Child: The Neo-Human Empire have no compunction about harming the children of the Youth League, or any other children for that matter.