Review of Casshern Sins
This anime is unique in many aspects. People are thrown into confusion by it's focus. There is, essentially, no story line or plot in this anime. What this anime attempts to do is delve into the nature of death, and the meaning of life. It is important to realise that the characters, and their stories, are not only the focus of the anime, but the only thing that drives what little plot there is. Spoilers A few things that need to be clarified in my opinion is the confusion around luna's eternal life giving, the ruin, and Casshern's final decision. Luna only wants to givelife eternal because she is simply afraid of death. However, the way she does this is curing the Ruin by giving people her blood which we are told contains nano-machines which will repair robots. This repairing is what brings the robots back to their normal state of immortality, which we are told robots had before the Ruin. So Luna does not have some 'magical power' which gives life, she is simply repairing the decay that is occurring because the world is Ruined. However Casshern, who we are repeatedly informed is the God of Death in everyone's opinions, both for his bodies innate strength and destructive power, as well as the fact that he caused the Ruin by slaying Luna. Casshern, after travelling and bearing witness to the numerous stories of people striving to live to the fullest before they are consumed by Ruin and die (imo ruin can simply be substituted for death or ageing) realises that what makes these people work so hard, and accomplish so much, in essence, live, is the fact that they are aware of their own mortality.
So when Casshern finally encounters Luna, he, and his companions, realise that this 'gift' of eternal life, could also be a curse. Because if you live eternally, and have no fear of death, your life loses meaning. You have no fear, no motivation nothing. This is also, though not clearly, shown by the episode where they pass through the circus like town that has grown up around Luna. It's full of what most people would call insane people. We see the robot repeatedly throwing itself from a building, (more robotically than any other robots have acted in the show) purely because it can not die. This is the effects of Luna's 'eternal life'. And Casshern, Lyusa and Ringo decide that it's, as Ringo says' "Unnatural". So they leave because it is their ability to die which gives meaning to their life. However after Ogi and Lyusa die, Casshern leaves Ringo to face Luna again. They meet and Luna stabs Casshern. And, just like we were shown 20 something times at the start of each episode, their blood mixed. Casshern's nature of 'death' corrupted Luna's nature of 'eternal life' resulting in robots gaining mortality. So instead of just killing everything instantly, or everything living meaningless lives forever, Casshern compromises. He lets Luna give life, and in return, when those lives have 'used up' their meaning, or as the show says 'forgotten death' Casshern will come and kill them. Their fear of him, the fear of death, will provide the meaning to the eternal life that Luna can provide.
A final point that was shown even in the final episode, and as the credits rolled, is Ringo's apparent ability to survive the Ruin. It is quite possible she is a Cyborg, or essentially Casshern Sins perfect being. Not only are we shown her to be rusting, but she also bleeds (which only she, Leda Dio and Casshern do aside from Ogi for some reason) There is also the scene in Ogi's backstory where he finds here hidden in a robots body and says something along the lines of, she seemed to be both Robot and Human... and what's that called? A cyborg. What this means, is that as a robot, she can survive the Ruin because of Luna's nano-bots, but as a human she will still age and eventually die. (as the fact she is shown to be the only robot to grow up). She also hints that 'the others' will eventually become like her. What this means i don't know. but it suggests that other robots are accomplishing what Braiking Boss and Ogi started, making Robots into 'God's' beings that will live, age, reproduce, and die. (As a side note, I think that was the meaning behind Leda's character. I believe her despair at not being able to be a mother, which she was created to be, has led her to seek beauty. But that selfishness corrupted her until Dio's example of caring for her changed her priorities from selfish vengeance back to a love for another, which is why they were shown to die so peacefully with each-other.)