collusion; conspiracy; secret agreement
Refers to two or more parties secretly cooperating for a dishonest or improper purpose, often in business, politics, or competitive settings.
The company is suspected of collusion in the bidding.
There seems to have been collusion between the judges and the contestants.
illicit sexual relationship; liaison; common-law marriage
Older or literary term for a secret romantic or sexual relationship, sometimes implying an improper or informal union. Modern usage is rare; more common terms include 不倫 or 内縁関係.
Old novels often depict illicit liaisons between men and women.
なれ合い describes a cozy, mutually convenient arrangement between people, whereas 癒着 is stronger and often used of organizations or institutions with implications of corruption.
common-law couple; couple in an illicit union
Standard kanji spelling for both senses.
Mixed kana-kanji spelling; less common but seen in practice.
Kana-only spelling; used when the kanji 馴 is not preferred or for clarity.
Derived from the verb 馴れ合う (to become familiar with each other and act in concert), from 馴れる (to become tame/familiar) + 合う (mutual). The noun form 馴れ合い originally meant 'becoming familiar with each other' and developed the negative connotation of improper collusion or secret intimacy.