If Keyaru could turn back time and keep his memories the first time, then is there a reason why he can't turn back time again and have everyone else maintain their memories?
I haven't read the WN for this series but I'm reading the LN and the manga seems to be fairly consistent with that. As an active LN reader, it seems to be the case that the manga and anime (if it has it) for any given series is typically adapted from the light novel if there is one
This was actually the reason I dropped the light novel after finishing the first volume. I can appreciate the political/strategic aspect somewhat, but focusing on it to the point where it detracts from the current events just felt off to me. For the record, I regularly read other light novels...