(n)person in charge (of an area of work, but not necessarily supervising other staff); person responsible; one in charge; responsible party; contact (person)
合併その他の交渉のために同社は25人の担当者を加えた。 The firm has added 25 new associates to work on mergers and other deals.
When I reached the hall right away the person in charge unrelentingly said things like "This painting is certain to increase in value in the future," and I went and signed the contract.