In a dark future, the world is in ruin and everything is slowly crumbling away into dust. Humanity is almost extinct, while robots desperately seek out new parts to replace their rusting bodies. Their only hope for survival is to devour the one known as Casshern… or so they believe. Meanwhile, Casshern himself has lost all memory of his past. Why are these robots attacking him? Did he really kill the one known as Luna; the Sun that was called Moon? And why is he, alone, unaffected and undamaged by the ruin?
Earth is under attack from the alien invaders known as the Radam and is quickly losing the battle. With the planet’s finest defense, the space ring, being overrun without much opposition, mankind’s fate seems bleak. One of the few forces left to oppose the Radam are the Space Knights; but they are anything but successful. That is, until a mysterious man named Blade falls from the sky. Blade has the power to transform into a Tekkaman, one of the deadliest fighting forces in the universe – the very force that is leading the Radam onward! But unlike the other Tekkamen, Blade is obsessed with just one goal: defeating the Radam. Having lost his memory, he doesn't know why, but he knows he must stop them. With the help of the Space Knights he can begin uncovering his past, discovering who the Radam and the Tekkamen are, and of course, save Earth in the process!
Lots of similarities between these two. Main characters Takaya "D-Boy" (Blade) and Casshern aren't exactly normal humans and both are very indifferent to their surroundings, but develop and change a lot. They're very powerful delivering fast paced and over the top action. Both shows heavily emphasize strong rivalries with villians that are very similar to the main characters, with Blade vs Evil, and Casshern vs Dio. Both shows feature gritty, grimdark, and post-apocalyptic settings with similar pacing. To top it all off, they share the same composer Kaoru Wada, his music in both is very similar and incredible. Fun note: Seiyuu Toshiyuki Morikawa (whom supposedly broke two mics with his voice during Tekkaman Blade) = Blade and Dio.
Simon lives a boring life in the underground village of Jeeha, where his main job day in and day out is to dig tunnels. His close friend Kamina, however, longs to bust out of their oppressive existence and reach the surface world where open skies and adventure await! One day, during his usual digs, Simon discovers a robot with a big face buried amongst the rocks. No sooner has he shown Kamina his mysterious find when two beings from the surface crash land into Jeeha Village - one is a gun-toting woman calling herself Yoko and the other is a terrifying mecha piloted by a Beastman! Seeing their chance to escape village drudgery, Kamina rallies Simon and Yoko to defeat the invader using their new robot, Lagann. However, upon breaking out onto the surface world, Simon, Kamina, and Yoko encounter enemies more powerful than they could have envisioned. Their fight for adventure just turned into a war for the survival of the human race - will their lust for freedom hold out against such terrible odds?
Assuming you loved the shounen action and gorgeous stylish animation, the zany 70s concept, I highly recomment Tengen Toppa Gurren-Lagann. One thing to note is that Gurren-Lagann is far crazier, more spastic, but also has a more powerful story that is gripping from beginning to end. Gurren-Lagann, like Casshern Sins, has style by the bucket-load, and its shounen approach is far more brazen. Worth checking out if you want to keep the style and action of Casshern but want to discard the episodic philosophising.
In an experimental city of despair and carnage, ORGAN will do anything necessary to gain power and wealth. Unfortunately for one underground boxer who was mutilated, a rogue doctor has given him what ORGAN specializes in and he despises: Texhnolyze body parts. Will these cybernetic appendages help exact his revenge upon the one who made him this way?
The two series, despite their differences, have a key similarity, which only becomes apparent well into the episodes. Both with Casshern Sins and Texhnolyze, the focus eventually shifts to the struggle against the inevitable. Without spoiling anything, I have to say that a great deal of information is required, fully, to understand this and the final, and most important, pieces of the puzzle can only be acquired by concluding the two series. It is safe to say that with a little difference, about 3/5 of the episodes of both titles set the stage.
It is not recommended to attempt to watch either one of the two without the requisite patience and here is a caveat: they accelerate very slowly towards the ultimate conclusion. It is also not recommended to watch an episode a day or even two or three, especially with Texhnolyze. The reason is simply that the intensity of the emotions conjured up would be diminished if not negated altogether.
Provided the above advice is not disregarded, it is more likely than not that the viewer will derive a good degree of pleasure with a bit of emotional masochism of the intellectual variety.