You're probably right aha, but it's just one of those trivial things I need to know more about lol.
Who knows, we might still learn more about it in the future. Like I mentioned yesterday, the fact Miura cut the visit to Hanarr short and then showed us the sequence of events like he did in this episode implies to me that he's got a specific way in which he wants things to be revealed to us. See Griff and I's talk earlier about how action and story go together in Berserk. All stories have a rhythm that's kind of like an ebb and flow: things are set up and then at some point there's an escalation towards a climax where they pay off. Right now they're still being set up. We're heading to a big reveal about the Skull Knight's past and the Berserk's armor, and a part of that reveal may be related to the current state of SK's armor.
Overpower in the sense of remaining in the Moonlight Boy form by choice and not reverting back to Femto when the full moon ends. I definitely didn't explain that very well in my post. [...] I'm wondering if Femto can be kept at bay even after the full moon with the help of the guru's magic while he is on Elfhelm.
Ah, I see. Well, I don't think so, or at least not in a manner that they could control without problems. Otherwise we're really close to the end of the story, aren't we? Guts, Casca and their son can spend the rest of their lives on this beautiful island, safe from harm. Cut to credits. So, yeah, that's not going to happen. Even if they did have that ability, something would have to prevent or disrupt it.
What could happen, which I speculated about a while back when episode 358 came out, is for them to try to keep the boy on the island beyond his allotted time, and for him to revert back. Now how about that for a dramatic reveal? It could be something as simple as Danan putting him to sleep alongside Casca at the end of the night. Or things could go in the opposite direction, with someone feeling suspicious and magically forcing him to revert.
But it could also go very differently. For example the boy's nature could be intuited or revealed, but without him actually transforming back. Then, later on, Griffith could return with apostles in tow to neutralize that threat. It would provide an opportunity for a stalemate of sorts, where Griffith's forces would be defeated, but he himself would only be stopped from killing everyone by the boy's love for his parents, leading him to retreat.
That would be a perfect launching point (after a period of rest) for the final journey: to go and confront Griffith, not (just) for revenge, but to save the boy... and incidentally to save the world too. Because only they can do it. It could also come to light that the boy doesn't have long before he's eventually erased, if we want to add a supplementary pressure.
And of course there are yet more possibilities, and many more things I'm skipping here for the sake of keeping it simple. To quote something I said two years ago:
Keep in mind that Guts and Casca's reunion may have started, but it certainly hasn't concluded or even proceeded forward yet. And said reunion will be one of the most important moments in the entire series. What we've seen so far was amazing, but we've yet to see the crux of it. Beyond that alone, Elfhelm was always set out to be where a lot of turning points would happen. More information about how the world works and how it is changing. Reveals about the God Hand's plans and maybe how to stop them. Key character development for Guts' group. More information about the Skull Knight and what happened a thousand years ago. A new, different reason for Guts and the others to go after Griffith. And so on.
I believe a lot of these developments will occur in short succession. You could say it's already started (Casca being restored, the beginning of Griffith's empire, the first glimpses of SK's past), but more is to follow. The next 20 episodes are going to be quite the ride.