noun
bad friend; undesirable companion; bad influence
Refers to a friend who is a bad influence or leads one astray. Often used in contrast with 良友 (good friend).
See also: 良友
彼は悪友に誘われて、よく夜遊びに出かける。
He often goes out at night, led astray by his bad friends.
悪友と付き合うと、自分も悪く
They say that if you keep company with bad friends, you'll become bad yourself.
noun
partner in crime; close friend; buddy
Jocular or affectionate term for a close friend with whom one shares mischief or secrets. Not truly negative; implies a bond through shared (often minor) misbehavior.
彼とは学生時代からの悪友で、今でもよくつるんでいる。
He's been my partner in crime since our school days, and we still hang out a lot.
悪友たちと夜遅くまでゲームをして遊んだ。
I stayed up late playing games with my buddies.