In a futuristic Earth, robots have been constructed to help mankind and preserve the planet – but their plans went terribly, terribly wrong. Led by the android designated BK-1 – more commonly known as The Black King – these robots have since taken over the world and enslaved mankind, believing that destroying humanity is the only way to save the planet. Thankfully, there is hope: Tetsuya, the son of BK-1's creator, has given up his humanity to become the cyborg Casshan; with the help of his robotic dog Friender and his once-girlfriend Luna, Casshan will fight to clear his father’s name and put a stop to the robots’ murderous rampage.
Source: Anime-Planet