go-between, broker, proxy, middleman
儈 centers on a person who acts as an intermediary in transactions or arrangements: a go-between, broker, proxy, or middleman.
儈 combines 亻 (person) with 會, which likely contributes the sound and the idea of meeting or gathering, suggesting a person who brings parties together.
A person 亻 who arranges a meeting 會 between two sides: a broker or middleman.
For カイ, imagine a broker buying and selling kai (shellfish) at a bustling market: kai -> カイ, and the person 亻 is the go-between.