Translation guide
A sexual partner without romantic commitment. Japanese has several slang terms, ranging from casual to crude. The most common and versatile is セフレ (sefure).
fuck buddy
Most common, casual slang. Abbreviation of セックスフレンド.
A friend with whom one has sex without romantic involvement.
Abbreviation of セックスフレンド. Very common in casual conversation among younger people. Neutral to slightly crude.
That person is just a fuck buddy.
He said he wants a fuck buddy.
The full form of セフレ. Slightly more explicit, but still common.
We have a fuck buddy relationship.
Literally 'sex friend'. A more direct Japanese coinage, but less common than セフレ. Can sound a bit stiff or euphemistic.
He's looking for a fuck buddy.
Explicitly crude ways to refer to a fuck buddy, often used among close male friends or in vulgar contexts.
From やる (to fuck) + 友 (friend). Very crude and masculine. Not used in polite company.
Extremely vulgar. Use only with very close friends who appreciate crude humor.
That guy apparently has several fuck buddies.
Direct loan from English 'fuck friend'. Less common than セフレ and sounds more explicit/foreign.
He says he wants a fuck buddy.
Softer ways to describe a casual sexual relationship without using explicit slang.
Literally 'a body-only relationship'. Describes the nature of the relationship rather than the person. Can be used in more serious or explanatory contexts.
I have a purely physical relationship with him.
Literally 'a clear-cut relationship'. Implies a pragmatic, no-strings-attached arrangement. More about the mindset than the physical aspect.
All direct terms for 'fuck buddy' are slang and should not be used in formal or polite situations. In such contexts, describe the relationship indirectly (e.g., 体だけの関係) or avoid the topic. Using セフレ with strangers or superiors can be seen as crude or inappropriate.
I'm not in that kind of relationship with him.
セフレ is the most common and natural in casual speech. セックスフレンド is its full form, slightly more explicit. 性友 is a Japanese-made word that is less common and can sound awkward or overly literal. Stick with セフレ for most situations.
Let's keep this as a no-strings-attached relationship.