I don't know, This is the point where Okaiken (Mitoyagi back then) forks away from Real Japan... hence the last blank area of the Okaiken wiki page. I think there could be several options into this, not just bomb Okaiken (remember that 1 month 1 week gap between the last bomb and the Showa Emperor's surrender message? That actually give us an idea that maybe the bomb was not the cause of the end of WW2 after all. After Japan lost Okinawa, the Japanese considered surrendering. Also, we can choose a treaty rather than surrendering, as that would make sense for the next phase of Okaiken's history, which is the Quiet Revolution and the current constitution.