@Kredim Thanks for another quick translation! And so we steadily go back into wordier chapters...
If you'll permit me, some pointers:
Page 7, Last panel, 1st bubble
I think the vibe here is while Yayoi is thrown for a loop, uncertain and actually scared by this development, New Emperor switched arms from sword to bow, possibly showing he accepts the duel in Tai Sui's eyes. So maybe:
[..so you accept, huh?]
Page 14
I believe the 己 here is directed at the dying villager, not at Masakado himself. So it's more like:
[Ridiculous…] [more than the pillaging...] [more than their (own) pain...] [that (loss of Masakado's reign) is what you regret?]
Accordingly, if we stick to the interpretation that this story's Masakado is the kind to fight for his people, then perhaps the usage of 朽ちて here isn't "to be forgotten", but "rot/die". As in, Masakado regrets more that he couldn't do more for his people.
So perhaps
[I cannot... rot away/die like this]
Page 39, 1st Panel
I think あらゆる全て ("everything") here is relative to おいてでも, and not to 島国の猿共 . Perhaps it's more like this?
[...unforgivable.] [I will not forget this, you island monkeys...] [Even if I have to leave everything behind, I swear you will face my wrath]
EDIT: after checking reactions on Japanese and Chinese fanbases, yeah no one there were under the impression main Tai Sui is out to massacre all of Japan, just our group