Casshan: Robot Hunter is the English title of a 4-episode OVA, a retelling of an anime series known as Neo Human Casshern.
In a World devastated by a Robot War, humanity clings to existence, enslaved by a society of Ridiculously Human Robots backed by Mecha-Mooks, all under the command of the dreaded Black King-1, the robotic tyrant who overthrew humanity. Into this wasteland wanders a stranger, a wandering without name or past. Casshan, the title Robot Hunter — an incredibly powerful cyborg with a hatred for all Neoroids and a burning desire to slay the Black King-1.
Over the course of the four episodes, Casshan is eventually revealed to be Tetsuya Azuma, son of Dr. Kotaro Azuma, the scientist reviled by humanity for creating the Neoroids and particularly the Black King-1. Mortally injured early in the uprising, Tetsuya converted himself into a cyborg warrior so that he could destroy his father's creation.
Galvanised by chance interactions with some of the few remaining human fighters, Casshan finally confronts his archenemy in a battle neither of them can survive...
- Artificial Human: Casshan. A Ridiculously Human Robot of the "Cyborg driven by a Ghost in the Machine" variety.
- The Black King-1 and his most elite androids, or "neoroids", are clearly made to look like synthetic humans, in contrast to the more obviously machine-like mooks.
- Ascend to a Higher Plane of Existence: Implied; after Casshan kills Black King-1 and triggers the neoroid shutdown sequence, Tetsuya's soul is shown rejoining that of his parents and the three fade away into brilliant light, in between shots of the shutdown sequence activating.
- Bittersweet Ending: Casshan kills Black King-1, ending the neoroid threat, saving humanity and freeing the spirits of Tetsuya and his parents. But he dies to achieve this, and because he was always a lone wolf, his role in freeing humanity goes unknown, save by his former girlfriend Luna, who has now lost her beloved a second time.]
- Blasphemous Boast: At one point, Black King-1 brags that if there is a God, then He must be an android.
- Breath Weapon: Invoked. The Black King-1 has a small but powerful laser turret concealed in his mouth.
- The Caligula: It's implied throughout the first three OA Vs that Black King-1 is unhinged, but the fourth confirms it, showing that he keeps a mindless robotic copy of his creator repeating his original programming instructions on loop on a hidden throne that he worships like an idol, and him revealing he has even gone so far as to trap his creator's mind inside his own. When Casshan shows up for their final confrontation, he starts ranting about being a heaven-sent savior that humanity has secretly been praying for, and curses them for wrongfully declaring him a "devil" instead.
- Compilation Movie: Casshan: Robot Hunter is actually a series of four OAV episodes merged into a single movie.
- Dub Name Change: The Japanese name of Braiking Boss is converted into English as "Black King-1", often forgoing the "-1" suffix.
- Full-Frontal Assault: Black King-1 is stark naked during his final clash with Casshan.
- Gaia's Vengeance: Black King-1 was created to spearhead an environmental restoration program, and he justifies his conquest and near-extinction of humanity as the only way to save the planet from humanity's abuse.
- Ghost in the Machine: After going rogue, Black King-1 killed Kotaro Azuma and his wife Midori Azuma before transferring digital copies of their consciousness into machines; Kotaro into the Black King-1's own cybernetic brain, and Midori into a robot swan.
- Despite being called a cyborg, Casshan seems to be more a machine with Tetsuya's brain patterns uploaded as its AI rather than an actual melding of flesh and metal.
- Godiva Hair: During the execution Luna's hair perfectly covers her nipple in most close-up shots. Only when she's mentally saying goodbye to Tetsuya does the wind leave the breast completely bare.
- Gorn: Casshan: Robot Hunter milks the fact all its enemies are Mecha-Mooks for all it's worth. Casshan literally tears his enemies apart with his bare hands — the first OVA has one Ridiculously Human Robot get its eye punched so hard it smashes, and then his head is literally ripped off of its shoulders and presented to its master, artery-like wires and cables dangling, living long enough to gurgle a final hail to the Black King.
- Heroic Sacrifice:
- A Resistance pilot injured after their helicopter is shot down orders Luna to leave him behind so she can reach the rendezvous point and get the plans for her MF Gun to the rest of the Resistance. He lures an android patrol in close, then blows up explosvies concealed around his resting place.
- The leader of a band of Resistance fighters gives his life to trigger a bomb intended to be used to destroy an android war train.
- Friender is seemingly destroyed saving Casshan from a kamikaze robot, leaping over a cliff with it into the ocean far below then never reappearing after it explodes.
- Casshan manages to defeat the Black King, but at the cost of his death.
- Hybrid Power: Due to Casshan being a cyborg, the MF Guns which can one-shot standard androids have no effect on him.
- La Résistance: Luna works for them, and supplies them with the plans to her anti-robot gun.
- Load-Bearing Boss: Justified. Because the Black King-1 neoroid was created to be the central control unit for all androids, a system was put into place where deactivating the Black King-1 would trigger a global shutdown of all other androids. The final OAV revolves around Casshan attempting to kill Black King-1 and trigger this failsafe to prevent him from annihilating the human resistance.
- Monstrosity Equals Weakness: Zigzagged. The generic robot mooks are all extremely inhuman-looking, ranging from hulking behemoths with rocket-propelled spiked piledrivers for hands to spindly bipeds with camera-like heads and machine guns in lieu of arms. But the more human-looking neoroids who directly report to Black King-1 really aren't any tougher than their monstrous underlings, and Casshan tears through them all with equal aplomb.
- Punch Parry: The final battle between Black King-1 and Casshan boils down to them throwing one single final punch with all of their strength. Their fists meet squarely and lock together, struggling as they try to overpower each other. In the end, Casshan wins; his fist smashes Black King-1's arm into pieces and continues traveling to punch a fatal hole through the Black King-1's chest.
- Putting on the Reich: The Black King-1's "Andro Corps" empire has very strong overtones of Nazi Germany. Even his symbol, a triangle with a secondary point jutting adjacent from each point, subtly evokes a swastika.
- Rewarded as a Traitor Deserves: Happens to the human prisoner who betrays Luna and his fellow prisoners' escape attempt, under the assumption that he'd be freed.
- Rocket Fist: The most basic mook is a hulking semi-humanoid with a spiked disk for a "fist" that is tethered to the arm by cables. To attack, rockets concealed inside the fist detonate, launching the spikes at incredible speed at a target, whereupon the cables reel it back into its firing mechanism for a fresh shot.
- Samus Is a Girl: Luna is initially introduced wearing a full-facial helmet and with her body obscured by a heavy hanging cloak, to the point she is mistaken for Casshan in-universe until she lifts her helmet and reveals she's a pretty young woman underneath.
- Shameful Strip: Happens to Luna while she's imprisoned on a crucifix.
- Shout-Out: When dressed in his uniform, Black King-1 looks a lot like M. Bison, as seen in the Animated Adaptations of Street Fighter II.
- Shrouded in Myth: The Black King doesn't even believe that Casshan exists until the end of the first episode, and most of the other characters think of him as a legend until his Big Damn Heroes moment.
- Spikes of Villainy: During the final battle, Black King-1 randomly sprouts crimson, crystalline spikes from his shoulders, thighs and pectorals.
- Suicide Mission: Whilst Casshan's mechanical body may give him Super Strength and Super Toughness, he doesn't have any kind of self-repair system, nor does he have access to any kind of lab to report back to after battle. As a result, damage from his fights accumulates over time, and eventually he reaches a point where his systems are shutting down from the accumulated faults. His final attack on Black King-1 is suicidal because he knows he's going to go offline permanently either way.
- That Man Is Dead: Casshan is adamant to Luna during the first two parts of the series that Tetsuya is dead and he is merely a mechanical copy.
- Torso with a View: Casshan and Friender tend to default to punching holes clean through their adversaries. Both the Black King-1 and his last neoroid subordinate, the sole female, both perish this way after Casshan punches holes clean through them.