彼はこの老舗旅館の十五代目当主だ。
He is the fifteenth-generation head of this long-established inn.
先代が亡くなり、長男が当主の座を継いだ。
When the previous head died, the eldest son succeeded as head of the family.
当主の許可がなければ、この蔵には入れない。
You cannot enter this storehouse without permission from the head of the house.