also: ちょくひ
noun
personal; confidential (on a letter)
Written on the outside of a letter to indicate it is personal and should be opened only by the addressee. Used in formal or traditional correspondence.
封筒に「直披」と書いてある手紙は、本人以外が開けてはいけない。
A letter marked '直披' on the envelope should not be opened by anyone other than the addressee.
昔の手紙には、よく「直披」や「親展」といった言葉が使われた。
In old letters, words like '直披' and '親展' were often used.