All righty, I got some sleep so I can put some thoughts together with some coherence.
Utawarerumono thoughts: Pretty fun game and wow did things go places towards the end. The scenes and happening after defeating Kuuya were a rollercoaster. I also really, really liked how all the Final Strikes and Co-Op Attacks had the dialogue and animation changed for the final battle to show the characters visibly sad and hesitant since they were fighting Hakuowlo. Camyu's was especially sad. The Eruruu/Aruruu one too, even though it's just a healing tech! Pretty good cast of characters though some were extraneous IMO like the archers and probably Kurou. One thing about the epilogue though Oboro such a jerk. Hakuowlo's dying wish was basically "take over Tuskur for me and lead the world to a new era."followed by a smash cut to Oboro deciding to just leave with Hakuowlo/Yuzuha's baby. Benawi would be the better ruler anyway so maybe it's all for the best but lol Oboro.
Not 100% clear on a few things and I don't know if later games address these, I was just dumb and missed it, or it was left intentionally ambiguous but My current assumption on the timeline is that Archaeologist!Hakuowlo found the "being" that I'll just call Uitsualnemetia. He made his pact with it after getting shot and got the mask. Then something happened to the Earth to drive humanity underground while Hakuowlo got entombed in ice (thought just occurred to be this could have been Uitsualnemetia being an asshole and interpreting "I want to sleep" by fossilizing him by causing a massive ice age and ruining the world rather than something more mundane like climate change, nuclear winter, or a meteor impact.) Anyway, humanity found Hakuowlo at some point, calling him Iceman and created the Decoys from him. Then the whole Mikoto stuff happened and Uitsualnemetia went ham, transformed a handful of the scientists into flesh blobs until Mutsumi tried to nuke him with a satellite on his request before settling on sealing him. I imagine Kuuya's tribe descended from whatever Decoys remained in the labs and eventually called humanity Onvitaikayan and actually had most of the details right, though heavily mythologized while those on the surface became everyone else.
Also as to a previous confusion I had, I guess Eruruu is just an ace liar and Aruruu really did almost die back during the invasion but Hakuowlo's power activated and he saved her again. ...And Mukkuru because again he totally took the brunt of that attack even if no one cared to mention him =(.
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xp1337: Don't you wish there was a spell-checker that told you when you a word out?