Half-face relationship
To barely know another person; to have met only once before
Neutral
我们只不过是半面之交，彼此是并不了解的 | Wǒmen zhǐ bùguò shì bànmiàn zhī jiāo, bǐcǐ shì bìng bù liǎojiě de
We are just casual acquaintances. We don't understand each other at all
[Source]
None
半面之旧 (bàn mián zhī jiù)
半面之识 (bàn mián zhī shí)
None
《三国名人序赞》(Sān Guó Míng Rén Xù Zàn), a work by 袁彦伯 (Yuán Yànbó) of the Jìn Dynasty (晋, 265 - 420)
During the Eastern Hàn Dynasty (东汉 | dōng hàn, 25 - 220), there lived a bright scholar named 应奉 (Yìng Fèng). 应奉 had a truly astonishing memory. Once, when he was twenty, he went to pay a visit to a government official at his home. When he arrived, someone stuck their head partially out of the door and told him that the official was not home. Tens of years later, 应奉 ran into that person on the road, recognized him despite only ever having seen half of his face, and greeted him