They felt like old friends even at their first encounter and they even became best friends.
Examples (Wiktionary)
Mandarin
一见如故
一見如故
yī jiàn rú gù
to hit it off
Mandarin
百闻不如一见
百聞不如一見
bǎi wén bù rú yī jiàn
seeing is believing (literally, “hearing something one hundred times is not as good as seeing it once”)
Mandarin
一见钟情
一見鍾情
yī jiàn zhōng qíng
love at first sight
Mandarin
故事讲述了灰姑娘在森林拾火柴时与王子邂逅,王子对她一见钟情。
故事講述了灰姑娘在森林拾火柴時與王子邂逅,王子對她一見鍾情。
gù shì jiǎng shù le huī gū niáng zài sēn lín shí huǒ chái shí yǔ wáng zǐ xiè hòu , wáng zǐ duì tā yī jiàn zhōng qíng .
The story depicts Cinderella's accidental encounter with the prince when she was picking matches in the forest. The prince fell in love with her at first sight.
Mandarin
你相信一见钟情吗?彼此对视1秒钟,来自对方的电流就会迅速穿越肉体直达心灵。
你相信一見鍾情嗎?彼此對視1秒鐘,來自對方的電流就會迅速穿越肉體直達心靈。
nǐ xiàng xìn yī jiàn zhōng qíng ma ? bǐ cǐ duì shì 1 miǎo zhōng , lái zì duì fāng de diàn liú jiù huì xùn sù chuān yuè ròu tǐ zhí dá xīn líng .
Do you believe in love at first sight? Looking at each other for one second, and the electric signal from him/her will rapidly pass through your body to reach your soul.