Written on June 24, 2019, this passage, based on an essay by Kadota Ryusho, sounds a warning that arguments in favor of accepting a female-line emperor could erode the unbroken imperial line from within and undermine the very legitimacy of the Imperial House.
Against the backdrop of positions advanced by the Japanese Communist Party, the Constitutional Democratic Party, and newspapers such as the Asahi and Mainichi, it reexamines the historical weight of the male-line principle and the efforts made by earlier generations to preserve it.

2019-06-24
If the imperial line of unbroken succession is broken, the very grounds of legitimacy of the Imperial House itself disappear, and it will be dismantled from within.
Japan now stands at a major crossroads because of the “enemy within.”

The following is from an essay by writer and journalist Kadota Ryusho published in “Shimbun ni Katsu!” under the title, Why Now a “Female-Line Emperor”?
Emphasis in the text is mine.
The Japanese Communist Party, which once openly called for the overthrow of the Imperial House, and the Constitutional Democratic Party, whose Diet Affairs Committee Chairwoman Kiyomi Tsujimoto once said in her own book of the Imperial House, “Don’t you feel a physiological dislike for it?
I mean, those people, that system, that family—I don’t even want to breathe the air near them,” have one after another come out in favor of accepting a female-line emperor.
Even though there already exist imperial successors, Crown Prince Fumihito of Akishino and Prince Hisahito, they are saying that they will revise the Imperial House Law in order to “bring forth a female-line emperor.”
Pushing both parties from behind are the Asahi and the Mainichi.
While the Asahi promoted this by introducing the words of a member of the advisory panel under the Koizumi administration that had recommended acceptance of a female or female-line emperor, saying, “At that time, the discussion should not have been stopped” (dated April 23),
the Mainichi, after quoting the words of a researcher whose view that “before the premodern era there had been no firm principle of imperial succession” is by no means an established academic theory, criticized male-line succession by writing: “ ‘The weight of the fact that male-line succession has been maintained from ancient times without exception…’
This is part of Prime Minister Shinzo Abe’s answer at the House of Councillors Budget Committee in March.
I certainly hope the discussion will proceed on the basis of a shared and accurate historical understanding” (evening edition, May 16).
Many people must have felt uneasy about this.
That is because it denies the one and only rule of the imperial line over two thousand years: the male line.
Our predecessors continued to make tearful efforts to preserve the imperial line through the male line.
When the 25th Emperor Buretsu passed away without leaving an heir, they invited an actual fifth-generation descendant of Emperor Ojin from the land of Koshi, present-day Fukui Prefecture, and enthroned him as Emperor Keitai.
Again, in the Edo period, in response to the concern of Arai Hakuseki over the extinction of the imperial line, the Kan’in-no-miya house was established, and in fact, seventy years after Hakuseki’s death, after Emperor Go-Momozono passed away without leaving an heir, Emperor Kokaku ascended the throne from the Kan’in-no-miya house and the line was handed down to the present imperial family.
Certain political forces are now trying to realize a female-line emperor even if that means disinheriting the male-line successors who have been preserved through such efforts.
It was the Sankei column of the 8th that pointed out the reason and background for this.
“To erode from within the ideology of ‘bansei ikkei,’ which is the very ground of legitimacy of the imperial system”—
this is a passage from the August 2004 issue of the monthly Sekai by the late constitutional scholar Yasuhiro Okudaira, the theoretical pillar of the Communist Party, who argued that the Imperial House and democracy cannot coexist.
If the imperial line of unbroken succession is broken, the very grounds of legitimacy of the Imperial House itself disappear, and it will be dismantled from within.
Japan now stands at a major crossroads because of the “enemy within.”
The people are waiting for newspapers capable of sounding the alarm about that fact.