The reason I think they might be the same soul is bc iirc The First made Mikaela from the Yu orb? The way I interpreted it was that by blending the light of the three big taboos he made darkness that God didnāt detect at first. He used the darkness to make Mikaela. And the Yu orb is like the personification of that darkness. To me this logic also helps explain why the Yu orb has independence bc how else could it create a soul for Mikaela if it wasnāt already capable of having one itself?? And if the Yu orb is just the consciousness of the nebulous darkness, perhaps thatās why God canāt simply kill it??? Idk if Iām connecting dots that shouldnāt be connected but thatās why I love hearing your takes lol. I especially appreciate you adding context to Gurenās actions bc I havenāt read Cat16, so your background definitely helps me understand things better.
Okay so I went to answer your new ask for this month and saw the end of it, so I looked again, and I just totally missed this ask somehow! Sorry about that! As such, I'll just respond to this one first and then get back to this month's.
Did Sika Madu make Mikaela from the Yu orb? I don't remember that, but my memory is honestly pretty bad, and I can't go back and look at those chapters at the moment. That would make sense though, so I'll run with it.
While I see what you're saying, idk if I'd say that necessarily makes Yu orb and Mikaela the same soul? Really, the Yu orb feels unaddressed in this regard. It's taboo to make life (and therefore create a soul), and so Sika Madu was punished for making Mikaela... but Yu is also right there?? No one except Mikaela and kinda Sika Madu even acknowledges that Yu has any form of sentience or life. Is Yu supposed to have a soul? It seems like the answer is yes? But then why does Sika Madu not get punished by having the Yu orb destroyed as well? God is implied to be omniscient here so you'd think God would know of its soul and have it destroyed?? That then leads to more of your ask, specifically how God couldn't kill the orb. That'd make sense, but afair, the angel in charge of punishing Sika Madu didn't even seem to try? Again, unless I'm remembering wrong, the Yu orb remains unaddressed there.
Ultimately, given that the Yu orb is ALSO reincarnating along with Mikaela, I feel like it's safe to say that it DOES have a soul (feels like I can never be 100% confident when it comes to OnS). While I still feel a bit doubtful that they have the same soul, I don't think you're connecting dots that shouldn't be connected. That's what theory crating is! Connecting dots that may or may not actually connect. You might be entirely right! If Yu orb and Mikaela have the same soul, that would make some sense as to why it goes unaddressed in everything I talked about above for one. I'd have to think on it more, but I think it's a good theory! Only time will tell whether you're right or not!
And no problem about the Cat16 stuff! It IS side content, so it shouldn't be necessary to understand the main story. I think it's important, but would agree that it isn't entirely necessary. However, as you say, it provides good context, so I'm happy to help provide that context for anyone who isn't familiar with it.