Confidential
noun, の adjective
If intimacy expands to something, that thing is confidential. Try visualizing intimacy as a sort of gooey liquid, expanding and covering a letter, and making that letter confidential.
親展 is generally written on the front of envelopes to indicate that only the intended recipient should read its contents.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
じゃあ、親展で送るね。
Alright, I'll send it as a confidential letter then.
検査結果は後日、親展で送付されます。
The test results will be sent to you later, marked “confidential.”
「親展」って書いてるのに、開けたの？これ、勝手に開けると、罪に問われるんだよ。
Did you open it even though it's marked “confidential”? If you opened it without permission, that could count as a crime.
親展の文字が印刷された封筒を買って来てくれない？
Can you buy me an envelope with the characters for "confidential" printed on it?