WARNING: the following contains spoilers for Platinum End Episode 24, "The Final Arrow," now streaming on Crunchyroll and Funimation.
The divine battle royale is over. Nakaumi Shuji became the new God in Episode 23 and became an ascended being in the distant heavens, and in Episode 24, the series finale, the new God grapples with the reality and responsibilities of his lofty role. Shuji's conscience begins to meld with that of the original God, and Shuji doesn't like it.
God-Shuji, however, lacks Metropoliman's arrogant god complex. Instead, the new God still seeks his own death, and not even the angels, such as Ogaro and Nasse, can stop him. The new God commits deicide on himself, and in so doing, reveals the truth of the God selection process. This was always meant to happen.
As a mortal boy, Nakaumi Shuji had longed to end his own life, until Kakehashi Mirai and Saki convinced him to live instead and play an active role in the God selection process. For a time, Shuji had been the favorite to be elected the new God, with Yuri and the playful Susumu supporting him. Then, after the battle with professor Yoneda, Shuji became the new God, and now, the Shuji-God in heaven is in anguish. He refuses to fully meld his mind with that of the original God, although he does converse with the elder God to gain some insights.
The elder God resolves the "chicken and the egg" paradox of God and humanity creating one another and explains that God had been created by another party, but not by humanity, which dispels Yoneda's "parasitic creature" theory. God really did create humanity on Earth, as God explains in Episode 24, and He even created the angel Nasse from a microscopic life-form found on the young Earth, serving as the template for all angels to follow.
God-Shuji, however, has no interest in watching over humanity any longer and takes action. He distracts Ogaro for a moment, then impales himself on a massive white arrow, ending his divine life with a single blow. At once, the angels dissolve one by one, and all humans on the Earth vanish, starting with the youngest. In God-Shuji's eyes, it's better for humanity to perish now to escape future pain, ending the cycle of misery and hatred on Earth once and for all. Shuji cannot find a way to save or protect humanity from its inner darkness.
As elder angels, Nasse and Muni die last and watch as the other angels, God and humanity all perish en masse. Nasse comments how this is what Muni, the angel of destruction, wanted all along, and Muni confirms it. This also confirms an earlier theory that Muni had been using Yoneda all along as a tool to destroy the heavens and slay God for good. Muni and Nasse then die as well, and the heavens crumble as Earth is stripped of all life. All along, Muni had been an agent of whatever entity or party first created the original God, and the goal had always been deicide. In the divine battle royale to choose the next God, there was never going to be a true winner.
Instead, the creator(s) of God seek their own death, and they envy humanity's ability to die. The creator(s) evidently used God, the angels and the divine battle royale to figure out a way to end their lives at last, with the battle royale being one giant experiment -- but it all ended in failure. Appointing a self-destructive God had been the means, but the creator(s) never achieved the ends, and they live on in despair, unable to bear their own immortality. They succeed in destroying God and humanity in Episode 24 but fail to get what they truly want, and so the creator(s) might simply move on to a new planet and create a new God to start the process all over again. But Mirai won't be around to see it.
