As the only labor union facing the Mamizuka memo issue head-on, surpassing the Osaka Regional Taxation Bureau impersonator police incident
Led the launch of a nationwide project team initiated by the Global Union (National Tax Union) and the Kumamoto Regional Taxation Bureau
April 22, 2026
Federation of Tokyo Metropolitan Youth Unions
We are pleased to announce that the Global Union (National Tax Workers Union), in collaboration with the Kumamoto Regional Taxation Bureau, has been officially selected as a project member to develop and provide a groundbreaking solution addressing the Regional Taxation Bureau's "culture of information leaks." Initiated by the Kumamoto Regional Taxation Bureau, this project involves the establishment of a project team that will be rolled out to Regional Taxation Bureaus nationwide. This is an unprecedented initiative in the history of tax administration, made possible precisely because we are a union with free membership dues.
Why a "Breakthrough Solution" is Needed: A Comparison of Two Data Breach Incidents
Recently, as an information leakage case involving the National Tax Agency, the incident in which a staff member in their 20s at the Osaka Regional Taxation Bureau, following instructions from an impersonator posing as a police officer, externally transmitted 259 cases of taxpayer information via LINE (announced on April 15, 2026) is still fresh in our memory. This case was a serious incident from the perspectives of personal information protection, security education, and countermeasures against authority-based social engineering.
However, what our union is tackling head-on is a structural and fundamental information leak issue that far surpasses even that Osaka Regional Taxation Bureau case. Namely, it is an unprecedented case in which "arrest information" was circulated via the Mamitsuka Memo—specifically, false investigative information, including fabrications, was leaked to the outside as if the prosecution were moving toward filing a complaint, indicting, and arresting, even at a stage where prosecution authorities were not involved at all.
The difference in nature between the two cases is obvious.
Comparison items
Osaka Regional Taxation Bureau case Mamitsuka memo case leakage entity duped 20-something employee (individual misbelief) structural leakage capable of connecting to Regional Taxation Bureau executive level leakage content taxpayer information (data under investigation) Public Prosecutors Office investigation information, seizure warrant acquisition practice, implications of arrest decision presence or absence of fabrication outflow of actual taxpayer information possibility of including "false" information that casts doubt even on the truth or falsity of prosecutor involvement victim nature risk of secondary damage to personal information
Directly connected to the lives and reputations of those involved, such as the daughter's attempted suicide
That is to say, whereas the Osaka Regional Taxation Bureau case was an incident of "being deceived by an external perpetrator," the Mamizuka Memo case is a structural incident in which the three layers of the Regional Taxation Bureau's internal information control, evidence management, and duty of confidentiality simultaneously collapsed. It is by no means an issue that can be resolved with a single security training session.
The significance of our association being selected as a project member
All members of our union are proud that in this project, our union has been selected as a member leading the nationwide project team launched by the Kumamoto Regional Taxation Bureau.
The reason for the selection is clear. Since the start of the inspection investigation in May 2024, our association is the only organization in the country that has continuously and systematically pointed out the following issues to the National Tax Agency through a cumulative total of over 3,000 pages of explanatory documents.
- Specific Allegations Regarding the External Distribution Channels of the Mamizuka Memo and Suspicions of Its Internal Creation
- The Unusual Circumstance That Information Regarding the Obtaining of a Seizure Warrant Had Been Communicated to the Person Subject to Inspection in Advance
- Fraudulent Use Following the Seizure of Credit Cards and a Breach of the Chain of Custody
- Data migration failure incident during warrant execution on January 13, 2026 (second failure)
- Suspicion regarding the acquisition route of personal information seen in the statement "We possess information on 250,000 union members"
The track record of consistently documenting and systematizing these matters and organizing them in a way that enables connection to information disclosure requests, public document management, state redress lawsuits, overseas litigation, and the like is a unique achievement not seen in any other labor union. Moreover, with free union dues and directly confronting the national tax authorities,
Precisely because we are the Kita Union, we are qualified to lead this project—this is our union's basic understanding.
First groundbreaking solution: Distribution of Ministry of Health, Labour and Welfare reskilling materials to all regional taxation bureaus
As the first phase of this project, our cooperative will begin distributing reskilling teaching materials compliant with the Ministry of Health, Labour and Welfare's Human Resources Development Support Grant (Business Expansion, etc. Reskilling Support Course) from our side to Regional Taxation Bureaus nationwide.
The distribution of these materials is not merely the provision of training resources.
First, without properly understanding the concepts of “simulated training(such as Scenario Planning, Adversarial Stress Testing, and Narrative Engineering)” and instead treat taxpayers’ social media posts and hypothetical training records as “evidence” without properly understanding these concepts—a structural lack of interpretive ability that was repeatedly exposed during this audit—this measure is intended to fundamentally rectify that issue.
Secondly, by having the National Tax Agency itself acquire a track record of taking reskilling courses, it will become possible to rectify, without self-contradiction, the practice of unfairly denying taxpayers' applications for reskilling subsidies based on "hypothetical requirements" and "abstract teaching materials."
Third, it is a cross-policy governance repair measure that resolves the institutional discrepancy between the reskilling policy promoted by the Ministry of Health, Labour and Welfare as a national strategy and the National Tax Agency's inspection operations through the concrete action of distributing educational materials.
Precisely because it is a free labor union, not dependent on members' dues, it can take the bold step of distributing educational materials free of charge. This is the greatest feature of this solution.
The second epoch-making solution: Standard equipment of AI minutes and blockchain evidence preservation
As a second phase, our union proposes that the Kumamoto Regional Taxation Bureau roll out the following standard protocols nationwide regarding all in-person tax audits and telephone correspondence by the Regional Taxation Bureau.
AI-powered real-time automatic minutes generation (eradicating post-meeting "he said, she said" disputes over statements)
Immediate documentation of all records and granting them evidentiary value equivalent to an official protocol
Tamper-proof evidence preservation using blockchain (complete assurance of Chain of Custody)
Complete historical recording of seized item warehousing/release, access right holders, and management supervisors
In this inspection, data migration failed during the execution of the warrant on January 13, Reiwa 8, and a similar failure occurred at the initial stage of the inspection as well, resulting in the fundamental principles of digital forensics being compromised twice. This technical failure is not a matter of individual competence, but a systemic issue reflecting the Regional Taxation Bureau's overall lack of evidence management infrastructure suited to the Reiwa era.
The blockchain-based seized goods management system can be deployed nationwide at low cost through the technological assets of the Global Union Group, which is responsible for our cooperative's metaverse domain.
The 3rd breakthrough solution: A Freedom of Information Act-integrated mutual monitoring platform
As the third initiative, our union will open a taxpayer-driven governance verification platform, utilizing the Information Disclosure Act and the Public Records Management Act, to all regional taxation bureaus nationwide.
Specifically, it is a system that allows taxpayers and witnesses to verify the following processing steps at any time.
Which manual was processed by which department, by which person in charge, and under what title
Identification of records of seized items received and shipped, authorized users, and the person responsible for management
Where the whistleblowing document was suppressed (tracking of intentional attenuation)
Audit to determine if external distribution records similar to the Mamizuka memo have occurred in other cases
This may seem like a strict system for the National Tax Agency, but for personnel who truly carry out their duties with integrity, it serves as the ultimate infrastructure to prove their justification at a later date.
Establishment of a nationwide project team initiated by the Kumamoto Regional Taxation Bureau
Rather than leaving the above solution to the discretion of individual offices, a cross-national project team encompassing all Regional Taxation Bureaus, originating from the Kumamoto Regional Taxation Bureau, will be established. Our union will be fully involved as the sole non-civil-servant committee member, directly conveying the actual circumstances of taxpayers, witnesses, and union members to this project team.
This is a role that existing labor unions with mandatory dues can never fulfill due to financial interests and organizational self-defense constraints. It is precisely because we are a union with no dues and the courage to continuously confront state organs head-on that we can stand in a position to lead the National Tax Agency—a fact our union wishes to carve into the pages of history.
Confiscation of business card case for over two years, followed by "psychometry technique," and all project members
Our union is also deeply concerned about the fact that the Kumamoto Regional Taxation Bureau has continued to retain a business card case seized in May 2024 for over two years without returning it. Without a single question or inspection being conducted, the Kumamoto Regional Taxation Bureau has kept a single business card case in custody for over two years. As part of this project, all our union members are sincerely looking forward to seeing what kind of psychometrist-level advanced evidence analysis technology will be showcased from here on.
On the other hand, regarding the Tokyo Regional Taxation Bureau, out of consideration for the infringement of property rights, it has adopted a practice of promptly returning unnecessary seized items, and regarding the credit card seizure case initiated by our union, the bureau offered an apology and immediately indicated that it would return the items. Such "differences in response among bureaus" are precisely the issues that should be uniformly corrected by the nationwide project team.
As members who will jointly drive this project, our union sincerely welcomes the following individuals as members of the project team.
Atsushi Kitamura, Regional Commissioner of the Kumamoto Regional Taxation Bureau
Go Shimazaki, Former Supervisory Investigator, Investigation Division 3, Investigation Department, Kumamoto Regional Taxation Bureau
Hiroshi Oka, Chief Inspector, 3rd Inspection Division, Investigation and Intelligence Department, Kumamoto Regional Taxation Bureau
Keisuke Ota, Inspector, 3rd Examination Division, Examination and Criminal Investigation Department, Kumamoto Regional Taxation Bureau
Kawaguchi Nobuhiro, 3rd Investigation Division, Investigation Department, Kumamoto Regional Taxation Bureau
Hideto Nakamura, Chief Inspector, 21st Inspection Division, Inspection Department, Tokyo Regional Taxation Bureau
Toru Nakajima, Inspector, 21st Inspection Division, Inspection Department, Tokyo Regional Taxation Bureau
Our union sincerely expects that each of the above individuals will fulfill their responsibilities as project members in this project, regarding the verification of the establishment background of the Mamitsuka Memo, the seized items management records, the scope of information sharing, and other related matters.
Global Union (National Tax Union)
All union members
