I haven’t seen anyone explaining this, and we’re past the era of fansubs containing translation notes at the top, so let me do the honor instead—
Lu Guang calls Qiao Ling “older sister.” Specifically, 姐 (jiě). He addresses her as “Qiao Ling-jie.” Here are two examples of him saying it in S1E1: (It’s not in the subs, so listen closely.)
This doesn’t mean they’re blood-related, though. Asian countries just like to express politeness/familiarity through family terms.
And assuming Qiao Ling and Cheng Xiaoshi are of the same age, then Lu Guang is younger than Qiao Ling, which means he has to address her with jie. However, since they’re close friends, he could’ve just dropped the jie. I mean, he doesn’t call Cheng Xiaoshi as “Cheng-ge,” does he?
Lu Guang keeping the jie for Qiao Ling but dropping the ge for Cheng Xiaoshi just shows how different his relationship is between the two of them. He’s more polite with Qiao Ling but more casual with Cheng Xiaoshi. And well, I guess it is kinda hard to address CXS as gege when he’s more like a child 🤣
But oh, it’s a different story if Lu Guang addresses Cheng Xiaoshi as “Xiaoshi-gege.” This one sounds more intimate, like how one would address their boyfriend. (And no, this is not meant to be kinky or whatever. It’s just the culture.) I don’t really know how to explain why this is, though. Just take it. [Tempting you guys to use it in fanfics (★‿★)]
