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matchmaker
go-between; intermediary; middleman; mediator; intercessor
「媒」 has another reading with different meanings.
親戚の叔母が媒を務めて二人の縁談をまとめてくれた。
A relative aunt served as matchmaker and arranged the marriage for the two.
昔は媒の紹介がなければ結婚相手に出会えない時代だった。
In the old days, it was an era when you couldn't meet a marriage partner without a matchmaker's introduction.
媒を通じた見合い結婚が今でも地方では珍しくないという。
It is said that arranged marriages through matchmakers are still not uncommon in rural areas.