WARNING: The following contains spoilers for Platinum End Episode 21, "The Time For Talk," now streaming on Crunchyroll and Funimation.
The heavenly battle royale has long since shifted into a Death Note-style battle of wits, which is the battle Kakehashi Mirai always wanted but may not be entirely ready for. He and Mukaido scored a violent victory against Metropoliman in earlier episodes, but now Mirai must fight on without Mukaido to aid him, and in Episode 21, he must make a decision once and for all.
Mirai aims to achieve personal happiness while protecting the happiness of the people around him, and he has a pacifistic approach to this plan. However, when Professor Yoneda declares his intent to strike down the parasitic God "creature," Mirai must take a stand and decide what's most important to him. And Nasse is watching.
As of Episode 21, Mirai and Professor Yoneda disagree sharply on what God's role in human society should be, if any. Professor Yoneda echoes Metropoliman's doubts about God and declares that God should be struck down so humanity can progress into the future on its own. Mirai, while not particularly pious, realizes that countless people around the globe rely on the presence of God through prayer and faith, and they would be lost if God were struck down. Mirai personally doesn't see the need for God for his own happiness and success, but as a true shonen protagonist, he doesn't just want to win -- he wants to win for everyone's sake, protecting everyone's happiness. Shonen heroes like him don't fight villains like Professor Yoneda for their own sake.
This is where Platinum End's Biblical themes about faith and God come into play. Yoneda strongly suspects that God is an artificial creation made from human emotions -- a benign but parasitic being that relies on humanity to survive, while Mirai doesn't care one way or the other. Mirai wants all pious people in the world to have faith in their traditional sense of God, even if the actual being might be an inert parasitic mass of emotions somewhere. Whether God is a literal being or not, countless people need it in their lives, and it doesn't matter to Mirai if the real creature is just some parasite. That does not justify deicide in Mirai's eyes, but he may have trouble convincing Yoneda to see things his way when they meet up at Japan's new national stadium.
In Episode 21, Professor Yoneda appears on the news and invites the surviving God candidates to join him at the stadium, similar to when Metropoliman invited everyone to join him at the Jinbo baseball stadium. Yoneda claims that he just wants to talk things out with academic discourse, but as Mirai may already suspect, Yoneda is up to no good. Professor Yoneda plans to kill Mirai, Saki and Temari with his white arrows, and then have himself and Shujin kill one another so that no God candidate is chosen to actually become God. It's unlikely that Mirai can convince Yoneda to abandon this plan and allow a God candidate to ascend to the heavens, and Mirai is aware of this as he joins Yoneda at the stadium.
Mirai vows that he will fight and try to take Yoenda's life if the latter refuses to help appoint a new God during this meeting. This is radically different from Mirai's previous attitude, where he insisted on pacifism no matter the threat to his own life, and it nearly cost him everything when fighting Metropoliman. Mirai hadn't been much of a fighter back then, but now he has the resolve of a warrior, and Nasse approves.
Mirai knows that this is the endgame, and for the sake of people's faith around the world, he cannot afford to hold back. He restrained himself even when the genocidal Metropoliman tried to take over the world, but even if Yoneda's plan is benign by comparison, Mirai cannot stand idly by. Clearly, this is what it takes to push Mirai into taking action, and the battle royale may soon resume. Whatever Mirai plans to do, he must do it quickly and without hesitation, or Yoneda will get the last laugh with his white arrows. Mirai's next move may be the one to decide this battle for all time.
