The background has the details! Those details tell the other side, previous world's happenings after the protagonists death, and that's clever. It's also fun to toss yourself around the areas, and it's just satisfying to hit the targets. As for the boss itself, I'm confused to how or when it becomes vulnerable. So in the end I wasn't able to beat it.
Still, I think the game captures the theme nicely with its lore, notably with the aforementioned regarding the background itself. It reminds the player somehow that the protagonist have already ended its previous life and this is the new one.