Here's my take, I don't think Suda is literally calling out actual mailmen as being psychopaths
I think the fact that the postal service happens to be the cover for the 25th ward's deep state is an allusion to Koizumi's postal reform (I think Ulmeyda in K7 and Destroyman in NMH are likely just echoes of the 25th ward, much like the full moon keeps showing up in every one of his games as a recurring theme from Moonlight Syndrome)
Koizumi was the leader of the japanese liberal party during the era in which the 25th ward would have been written (2005 - 2006)
https://en.wikipedia.org/wiki/Junichiro_Koizumi
One of the most important reforms he spearheaded was the privatization of the postal service
https://en.wikipedia.org/wiki/Japan_Post
https://www.ft.com/content/7d0dff74-04e ... 000e2511c8
https://www.researchgate.net/publicatio ... Japan_Post
Koizumi consolidated power within the liberal party by hand picking candidates that were supportive of his reformist policies. Which is what that wikipedia article I linked to earlier is referring to.
https://en.wikipedia.org/wiki/Koizumi_Children
(I'm just using wikipedia for convenience. I suggest you just use it as a starting point for your research because it's not like it's actually comprehensive or truthful.)
Koizumi was also responsible for sending the Japanese SDF on a foreign mission for the first time since the end of WW2, during the Iraq war, in an effort to keep close relations with the USA and the United Nations.
Now I can't read Suda's mind but I am assuming that's not something he approves of, considering the Liberal Party also appears in Killer7 (Hiro Kasai was an informant working for the Liberal Party, Julia Kisugi was hired by them and the two rapresentatives that are killed at the Mah Jong table are also from the liberal party) and by assassinating Fukushima (leader of the UN Party) in a power play they end up dooming japan to a nuclear holocaust lol.
I'm quoting from Hand in Killer7 here:
-------------------------------------------------------------------------------
A: THE UNITED NATIONS PARTY [APPEN-FAC-A]
-------------------------------------------------------------------------------
After the Second World War, the United Nations Party was founded by former mem-
bers of the Liberal Party. Since its establishment, it has become Japan's
leading political party. Toru Fukushima is the party's leader; he is a former
member of the Liberal Party. Some members of the party are older men, like
Hiroyasu Kurahashi and Shinya Akiba. The party also includes younger people,
whose leader within the party is Kenjiro Matsuoka.
When Fukushima was killed, the party briefly fell into chaos. Fukushima was
supposed to attend the Japan-U. S. meeting in the Kaku Building; in his place,
the Liberal Party sent its members. Negotiations between the Liberal Party and
the U. S. Government had concluded well before the meeting in the Kaku Build-
ing, so the meeting was intended to be a mere formality. Unexpectedly, the
U.S. Government broke off negotiations; as a result, both sides ended up kill-
ing each other.
-------------------------------------------------------------------------------
B: THE LIBERAL PARTY [APPEN-FAC-B]
-------------------------------------------------------------------------------
The Liberal Party is the second most powerful political party in Japan. Ohta
and Kuramoto (the men who attended the negotiations in the Kaku Building) are
members of the Liberal Party, and Hiro Kasai works as an informant for the Lib-
eral Party. Intent on destroying the U. N. Party, the Liberal Party wants to
reclaim its lost place as the forerunning political party in Japan.
The Liberal Party desired an extension of the Asian Security Treaty, and there-
fore kept its relationship with the U.S. Government in good condition. Oppo-
sitely, Toru Fukushima completely severed his relationship with the U.S. Gov-
ernment; he ended the security treaty in the interest of establishing Japan as
a truly independent state.
When the Liberal Party learned about Fukushima's annulment of the Asian Secur-
ity Treaty, it sent Julia Kisugi to assassinate him. As well, Kisugi was in-
structed to retrieve the Yakumo. The Liberal Party wanted to reclaim control
of the Japanese Government, to protect the Japanese people's interests. It
regarded Fukushima's action as reckless. Since the Liberal Party desired a
more complex relationship of support with the United States, it was only
natural that they should try to assassinate the leader of their Japanese
competition.
Kasai asked the Killer7 to eliminate Jean DePaul. He wanted the Japan/U.S.
Government meeting in the Kaku Building to succeed, in order to strengthen the
security treaty.
Fukushima, however, had known for years that the U.S. Government was plotting
against Japan. He took his anti-U. S. position in preparation.
The liberal party is depicted as the USA's lapdog, which would be consistent with mid-2000s japanese politics in which the liberal party was pushing for foreign military interventions in order to ingraciate the Bush government. In the end, despite pandering to the USA, when push came to shove the americans left the japanese out to die like dogs.
Considering Suda actually wanted to portray Matsuken as a positive character:
- Next, with "Sunset," the story is set in motion in earnest.
Here, I wanted to depict a Japan that fights to be strong, pitiably destroys itself, and is reborn from its ashes! In a sense, Japan is at its limit - and that's why I entrusted Matsuken with the task of representing the fighting Japanese.
- What's the point of Kun Lan's appearance in "Sunset"?
Matsuken is a the symbol of a nation, of a new Japan. Kun is a symbol of terrorism, and Harman is the will of the United States. It's meant to illustrate the sword of terrorism being offered to a nation.
The ideal being portrayed in his work seems to be that Japan should stand on its own, as a sovereign power rather than rely on the United States for help.
Unfortunately the translation of TSC and 25W doesen't make it very clear, but both wards are separate from the Japanese state in terms of governance system.
https://www.paradisehotel51.com/sin/202 ... planation/
They are both backed by ELBOW, which is described as a council of advanced nations. Meaning foreign nations to Japan, exerting influence over the japanese government by straight up brainwashing their children through the Maspro projects and the shelter children policy.
(This is made confusing by the english translation referring to Kaoru Hachisuka as the mayor of the 24 wards, when he's actually the mayor of the 24th ward only. By the time the 25th ward takes place in, it's implied that Yakuza have taken over the 24th ward after Hacisuka died and left a power vacuum lol.)
In short
the government of the 25th Ward is made up of Japanese people, who are actually aligned with foreign powers (ELBOW). Much like Koizumi was a Japanese PM, who was aligned with the United States and consolidated power by appointing political "assassins" to destroy the competition within his own party. Hence why I believe the usage of postal workers as a cover for the 25th ward's shadow government, might have been an allusion or critique of Koizumi's reformist policies (one of which being the privatization of the postal system.)
It is interesting to note that a similar plot point is brought up in TSC, with the FSO, CCO and TRO factions (which are NGOs) consolidated power over voting blocks through lobbying and the "volunteerization" of several government jobs. (Which basically means they hired most ex-state workers as "volunteers" due to their nature as non-profit organizations.)
I apologise if I was a bit unclear, I haven't really sat down to write an article about this for the website yet so all I have is a bunch of scattered notes but I hope I made myself clear anyway