noun
professional relationship ender; breakup agent
A person or agency hired to break up a romantic relationship, often by seducing one partner. The term is associated with the Japanese detective/private-eye industry and is not a neutral job title.
彼は別れさせ屋に依頼して、妻の不倫相手と別れさせようとした。
He hired a breakup agent to try to separate his wife from her lover.