I think forcing Japan to surrender at the end of WWII under the threat of Atomic Hellfire broke something in the Japanese national psyche.
They had a Warrior culture that saw surrender as the ultimate shame, something so bad that at Okinawa women were throwing themselves and their babies off cliffs rather than surrender. They also saw their Emperor as a living God, and then we glassed two of their cities and McArthur made Hirohito get on his knees and suck his dick and beg for forgivness (ok not literally but to the Japs national psyche it was as good as).
So you had this death before dishonor warrior culture that finds itself utterly humilated, their living God turned into a bitch, and to add to the injury they were forbidden to even
have any army at all by the new constitution forced on them.
So all these centuries of pride and tradition were erased with the stroke of a pen.
They were lost, so they turned to throwing themselves into work. Work and cooming and the more they felt isolated by Salaryman Culture and the more the birthrates went down the more they turned to cooming, and it got worse and worse, till now they're such an island of weirdos they have to have female only trains because they have perverts that take advantage of being crammed like sardines to dry hump womens legs as they are trapped, and the "keep your head down, dont stand out" culture means no one speaks up.
They've become a lost and increasingly degenerate nation, with the highest suicide rate of any industrialized nation on Earth, but their getting their own back because coomerism is contagious, its a mind virus, and with the rise of the interconnected world facilitated by the Internet, they're getting their revenge for Hiroshima by spreading and infecting us with their gross anime coomer shit.
You couldn't make this up lol