When I first started watching Casshern, I didn't really know what to make of it. It had its good moments, had some fantastic fights but the plot wasn't really going anywhere. Fortunately, I stuck it out and it delivers.
We see Casshern, Lyuze, Ringo and Ohji living happily together, growing flowers near the sea. All is well, until the ruin catches up to Lyuze and Ohji, at which point Casshern seems to go off on a rampage. Along the way he meets Braiking Boss (who finally atones for this sins), and then Luna. He then tells Luna that she should continue giving the gift of life and that he'll return "when they have forgotten about death". The episode ends with an adult Ringo, alongside Friender, musing on how she'll get to see Casshern again and what will become of the world.
Whilst most of the loose endings of the show are tied up, we still don't have some answers. What exactly is the ruin and how does Luna grant eternal life (beyond just giving her blood) are two of them. Yet, for all its ambiguity, I don't mind not knowing. It's just that kind of show. I'll miss Casshern, its been a good watch. Another season or even some OVAs would be great but how could they extend the story without losing the mood?