Self-Defense Law in Japan: Legal Boundaries for Civilians

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Introduction

In Japan, self-defense is legal — but it comes with strict boundaries. The self-defense law in Japan permits civilians to protect themselves and others from danger, but only when the response is immediate, necessary, and proportionate to the threat. If you go beyond those limits, you may face criminal charges, even if you acted out of fear.

Understanding these rules under the self-defense law in Japan is essential for anyone living in the country, whether you’re defending yourself on the street, in your home, or while helping another person in danger.

(This chapter is for educational purposes only and does not replace legal advice. For case-specific guidance, consult a Japanese lawyer.)

Core Laws You Should Know

Penal Code, Article 36 – Self-Defense (正当防衛) You are not punishable if you act to protect your rights (or someone else’s) from an imminent, unlawful attack, provided your actions are necessary. If you use more force than needed, it becomes “excessive self-defense” (過剰防衛) — in that case, punishment may be reduced or waived, depending on the situation.

Penal Code, Article 37 – Necessity (緊急避難)

You may take action to avoid a present danger, but the harm you cause must not outweigh the harm you’re preventing.

Penal Code, Article 35 – Justifiable Acts (正当行為)

Acts done under laws or legitimate business (e.g., security work) are not punishable.

Code of Criminal Procedure, Articles 213–214 – Citizen’s Arrest (現行犯逮捕)

Anyone may arrest a “flagrant offender” without a warrant, but must immediately hand them to the police or prosecutor. Using more force than needed to restrain them is illegal.

Minor Offenses Act (軽犯罪法)

Carrying concealed knives, iron rods, or other dangerous objects without just cause can result in detention or a fine — even if the blade is under 6 cm. “Just cause” means a legitimate, socially accepted reason (e.g., a chef transporting knives for work, a camper carrying tools).

Scenario-Based Guidance

Street Assault (Unarmed)

Allowed: Blocking, pushing away, striking just enough to break free, and escaping.

Not Allowed: Chasing after the attacker once they disengage, striking when the attacker is already on the ground, or retaliating after the threat ends.

Home Intrusion

Japan has no “castle doctrine” — the same rules apply at home as in public.

Allowed: Force necessary to stop an intruder’s imminent attack and secure your safety.

Not Allowed: Continued violence if the intruder is fleeing or no longer a threat.

Attacker Armed with a Knife or Stick/Bat

Because the danger of serious injury is greater, a stronger defensive response may be justified — but only if truly necessary.

Best Practice: Create distance, use defensive techniques to disarm or disrupt, escape, and call 110. Avoid unnecessary strikes after control is achieved.

Citizen’s Arrest

Only for flagrant offenders caught in the act. Use minimal restraint and hand over to police immediately.

Quick “Do & Don’t” Checklist

Do

Act only when the threat is imminent.
Use only the force necessary to stop the attack.
Disengage once the danger is over.
Call 110, secure witnesses, preserve CCTV or other evidence.
If making a citizen’s arrest, transfer the suspect to police promptly.

Don’t

Carry self-defense tools without a clear, legitimate reason and proper storage.
Chase attackers for revenge.
Assume home defense gives you unlimited rights — it doesn’t in Japan.

What to Say to the Police (Example)

In Japanese:「危険な状況だったので、自分（または他人）を守るために必要な行動をしました。脅威がなくなった時点でやめました。目撃者と防犯カメラがあります。」

In English: “There was a dangerous situation. I acted to protect myself (or another person) and stopped when the threat ended. There are witnesses and security camera footage.”

This makes clear that you acted under Article 36, used necessary force, and stopped appropriately.

Self-Defense Law in Japan | Case Study: Self-Defense on the Streets of Yokohama

In March 2021, the Yokohama District Court handed down a striking verdict that clarified how self-defense works under Japanese law.

Man punching another man in self defense in japan

The Case

In a trial over an incident on a Yokohama street, a man in his 60s who struck back after first being hit by a man in his 70s was charged with assault. On March 19, the Yokohama District Court (Presiding Judge Taro Kageyama) ruled that the requirements for self-defense had been met, and delivered a verdict of not guilty (the prosecution had sought a one-year prison sentence).

The case involved a 70-year-old man striking first, followed by the 60-year-old man hitting him back twice. The older man fell, suffering injuries including traumatic subarachnoid hemorrhage. He later died.

Why was the man in his 60s acquitted? Let’s break down the judgment and see the key points that led the court to recognize this as “self-defense.”

The Incident

One evening in February 2020, a man in his 60s (Mr. A) was walking home from work on a narrow sidewalk in Yokohama. From the opposite direction came a man in his 70s (Mr. B), who had been drinking heavily. The sidewalk was just 1.6 meters wide and cluttered with a roadside sign, leaving little space to pass.

As the two brushed close, Mr. B suddenly shouted at Mr. A: “What’s your problem, you bastard!”

Irritated, Mr. A turned and replied, “What?” in a low tone.One second later, Mr. B punched him hard in the face. Mr. A staggered back, bleeding from the nose.

Instinctively, Mr. A pulled his hands from his pockets and punched back twice — once with his left, then immediately with his right as Mr. B began to fall. Mr. B collapsed on the pavement. Shocked, Mr. A helped move him to the sidewalk and called 110 himself.

Sadly, Mr. B later died.

The Issue

The central legal question: Did Mr. A’s actions qualify as “self-defense”?

Penal Code Article 36 (1):

“An act unavoidably performed to protect the rights of oneself or another against imminent and unlawful infringement shall not be punishable.”

The Trial

Prosecutors charged Mr. A with assault (and even considered upgrading to assault causing death). They argued that hitting back twice was excessive and not motivated purely by self-defense.

But the court disagreed. After reviewing CCTV footage and medical reports, it ruled that Mr. A’s actions met all three legal requirements of self-defense under Penal Code Article 36:

Imminence – Mr. B had already struck first, and the danger had not clearly ended.
Intent to Defend – Even if Mr. A was angry, his primary action was defensive.
Reasonableness (proportionate) – Mr. A’s punches came instantly, in direct response to being hit hard enough to bleed. They were not seen as excessive.

The court acquitted Mr. A, declaring him not guilty.

Lessons from the Case

Self-defense is allowed in Japan when you are suddenly attacked, even if your response is strong.
Anger doesn’t cancel self-defense if the threat is real and ongoing.
Proportionality matters: Mr. A stopped once the attacker was down and even called the police himself — a critical factor in showing his intent was not revenge.
The case also shows that prosecutors can and do test the boundaries of self-defense in court, which is why clarity of your actions (and immediate reporting) is essential.