Deciphering the Criminal Responsibility of the "Dark Part-time Job" Instructors: The Heavy Cross of "Joint Principal Offenders" Unique to Japan

Deciphering the Criminal Responsibility of the "Dark Part-time Job" Instructors: The Heavy Cross of "Joint Principal Offenders" Unique to Japan

2025年06月13日 00:56

1. What is "Yami Baito"—The New Criminal Infrastructure Born from Anonymous SNS

In Japan, criminal part-time jobs collectively known as "Yami Baito" recruit perpetrators through SNS and anonymous chat apps using extremely short recruitment texts and the lure of high rewards. From special fraud roles like "receivers" and "senders" to cash transport vehicle heists and luxury watch robberies, "〆募集" posts on Telegram and X (formerly Twitter) serve as hubs, forming criminal networks with just a few clicks. According to the National Police Agency, the damage from special fraud involving Yami Baito in 2024 amounted to approximately 70 billion yen, with over 460 minors arrested.


While the executors dirty their hands, the directors send PDFs called "manuals" and Google Maps pins, never appearing on the scene. Physical arrests are becoming difficult due to cross-border IP masking and prepaid SIMs. However, Article 60 of Japan's Penal Code stipulates "joint principal offenders," allowing all participants to be punished as principal offenders if they have the intent to "jointly execute the crime," regardless of their role in execution, direction, or preparation.



2. Basics of Joint Principal Offenders—What is the "Mutual Utilization and Supplementation Relationship"?

The theory of joint principal offenders in Japan is explained by the doctrine of "mutual utilization and supplementation relationship." If A utilizes B's actions and B utilizes A's actions to complete a crime, the series of actions merge into a single crime, making each person responsible for the entire crime.

  • Case 1: Supreme Court Decision on March 31, 1950
    In a case where a yakuza leader ordered a subordinate to assault someone, the leader was found guilty of the same assault crime even though he was not present at the scene.


  • Case 2: Tokyo District Court on June 20, 2023 (the so-called "Luffy Incident")
    The defendant who gave instructions via LINE from the Philippines was sentenced to life imprisonment as a joint principal offender for robbery resulting in injury.

In Europe and the United States, individuals are usually sentenced separately for "incitement" or "conspiracy," but Japan characteristically imposes the "same sentence as the perpetrator" based on a result-responsibility principle.



3. Crime Types and Sentences Applicable to Directors

Crime TypesTypical ActionsStatutory PenaltyRecent Sentencing Trends
Special Fraud (Penal Code Article 246)Instructions to "senders" and "receivers"Up to 10 years imprisonment4 to 6 years even for first-time offenders
Robbery (Penal Code Article 236)Instructions for cash transport vehicle heistsLife imprisonment or 5 years or moreAggravated by the number of accomplices
Robbery Resulting in Death or Injury (Penal Code Article 240)Victim death in robberyDeath penalty, life imprisonment, or 6 years or moreRingleaders face life to death penalty


Even if the ringleader resides overseas, transfers and extraditions based on international criminal mutual assistance treaties are progressing. In a case of deportation from the Philippines, Japanese investigation documents were swiftly sent electronically, reducing the time to extradition decision to less than six months.



4. Key Points in Proving SNS Conspiracy—Communication of Intent "Beyond the Screen"

  1. Log Integrity: Access logs with timestamps issued by service providers lose evidentiary value if there are traces of tampering.

  2. Account Identification: Even when using VPN or Tor, if the device fingerprint (such as resolution or font information) matches, courts recognize the identity of the same person based on "high probability."

  3. Time of Agreement: In Japan, it is sufficient if the agreement is reached "before the crime is committed," and unlike the U.S. conspiracy law, a "clear step" (overt act) is not required.



5. When the Director Claims "Acted Under Threat"

Even if the executor claims "I was threatened that my family would be killed if I didn't do it," the mastermind, being the one who threatened, is rarely granted a reduced sentence. On the other hand, there is room for applying Article 68 of the Penal Code for "mitigation of punishment" or the Juvenile Law to the executor. UK criminal law acknowledges "duress," allowing for the avoidance of severe punishment, but Japan is cautious, considering "aggressive threats as self-invited acts."



6. Comparison with Overseas — The Key is Whether Sentence Adjustment Exists

  • United States: The RICO Act allows for the collective punishment of organized crime for up to 20 years, but indiscriminate application of aggravated results is rare.

  • Germany: Incitement (StGB §26) and aiding and abetting (§27) have "immediate reduction clauses" that reduce the maximum penalty.

  • United Kingdom: The 2016 Jogee ruling restricted "Joint Enterprise," changing it so that liability is only for "results within the scope of intent."

In Japan, joint principal offenders are held accountable for "all criminal results," which presents unexpectedly heavy risks for foreigners.



7. Five Points Foreign Residents Should Know

  1. Request for a Lawyer Within 48 Hours of Arrest: The court-appointed attorney system is available regardless of residency status.

  2. Right to Have an Interpreter Present: There are increasing precedents where discrepancies in statements due to mistranslation are rendered partially invalid.

  3. Revocation of Residency Status: Deportation is generally enforced if a sentence of one year or more is confirmed, even if suspended.

  4. Bail Amount Standards: For joint principal offenders in robbery resulting in injury, the standard is 5 to 10 million yen.

  5. International Lawyering: There are cases where home country embassies provide legal tech support, and early contact is effective.



8. Prevention and Platform Regulation

The Ministry of Internal Affairs and Communications revised the "Guidelines for Crime-Inducing Information Measures" in April 2025, shortening the request period for the deletion of anonymous posts from the previous 7 days to 24 hours. LINE and Yahoo have introduced AI moderation, automatically blocking 2,800 slang terms related to dark part-time jobs. While Telegram is reluctant to cooperate citing encryption, Apple and Google are nearing an agreement to suspend illegal recruitment accounts within 72 hours.




9. Conclusion — The Current State of Japanese Law in Judging "Invisible Accomplices"

In an era where crimes can be directed across physical distances and borders, Japan's joint principal theory functions as a net that does not let the director "behind the screen" escape. On the other hand, given the reality that executors may be minors or economically disadvantaged individuals, individualized sentencing and rehabilitation support are essential.To eradicate illegal part-time jobs, it is necessary for platforms, education, and international cooperation to function as a trinity, not just strengthening criminal penalties.



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