Some thoughts...
So Reg was sent upwards, from possibly below the 6th layer, to find "Haku" (ultimate value). I can only assume he was sent by Riko's mother to find Riko, but for what purpose?
By the time he reached the Narehate village, he had run out or almost out of "rewriter" (Incinerator) charges, so perhaps he used his last one to save Riko at the beginning of the story. If that's true, then a significant boost of electricity seems able to recharge it.
He lost his memory for some reason, I thought it was because of the first recharge but he recharged again at Bondrewd's place and didn't lose his memory, so perhaps he lost it somewhere between the 6th and 1st layer during his initial ascent.
When Reg met Faputa, he was speaking modern surface language, NOT the ancient language of Gabu and Vueko. He must have learned it from Riko's mother?
Did Faputa "do it with Reg" before he left, on page 39? What did she mean by this?
Neat that Faputa's "bra" is actually what looks like Reg's goggles. He also had some sort of stick or weapon on his back, wonder what that was.
Neat that Wazukyan* actually seems to be wearing a helmet of some kind, and his real head inside very closely resembles his human head.