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Proverb / Kotowaza

頭の黒い鼠

ReadingあたまのくろいねずみRomajiatama no kuroi nezumi

Refers to an insider, such as a family member or employee, who steals or embezzles from within.

a black-headed mouse

Quick Answer

Refers to an insider, such as a family member or employee, who steals or embezzles from within.

Literal Image
a black-headed mouse
How to Use It
Used to describe situations of internal theft, embezzlement, or betrayal of trust by someone close to the victim.

Meaning

When items or money go missing, people suspect animals or external causes, but this expression reveals that the true culprit is a human insider. It uses 'black-headed' to refer to human hair, likening a trusted relative, servant, or employee to a thieving mouse operating from the inside.

Literal Image

a black-headed mouse

How to Use It

Used to describe situations of internal theft, embezzlement, or betrayal of trust by someone close to the victim.

Tone

Critical and accusatory; it emphasizes the sting of betrayal by someone within one's own circle.

Examples

01

商品の在庫が合わないと思ったら、「頭の黒い鼠」の仕業だった。社員の一人が横領していたのだ

When I realized the product inventory didn't match, it turned out to be the work of a 'black-headed mouse.' One of the employees had been embezzling.

Learning Notes

Key Vocabulary

Estimated LevelN1Confidence: High
Estimate, not an official JLPT list

The vocabulary (head, black, mouse) is basic, but the metaphorical usage to describe internal embezzlement is an advanced idiomatic concept.

あたま / atama

head

黒い

くろい / kuroi

black

ねずみ / nezumi

mouse or rat

Usage Profile

NeutralCriticalCautionary

Usage note: This is a serious accusation of theft and betrayal; it should only be used when internal guilt is confirmed.

Misread Risk

Do not use this to refer to literal rodents; it is strictly a metaphor for human betrayal.

Search As

頭の黒い鼠あたまのくろいねずみatama no kuroi nezumiatamanokuroinezumiatama-no-kuroi-nezumiatama-no-kuroinezumi頭の黒い鼠 あたまのくろいねずみatama no kuroinezumi

Kanji in This Proverb

Related Proverbs

Similar身内の裏切り者
Similar内部の敵
Similar信頼を裏切る者

Origin

While real mice are covered in fur, the 'black-headed mouse' refers to a human with black hair. This expression is a euphemistic metaphor that identifies a human insider as the culprit in a theft, rather than an external intruder or a literal pest.

Index

Topics, Situations, and Tags

01

Topics

Social RelationshipsMoney and WorkTruth and Appearances
02

Situations

Explain an Unexpected OutcomeExplain Consequences
03

Tags

🐾Animals & Nature👥Social Dynamics💰Money & Business

Source Note

Where did this entry get its data from? The reference links are listed below. To understand how to read this section, see Data Sources.

Published
2026-03-15
Updated
2026-05-08
Source 1: tomomi965.comSource 2: tomomi965.comAbout Data SourcesReport a Correction

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