Find a ... fanfic?

I've got a phrase (and related character relationship) stuck in my head, but I can't remember where it's from. The phrase is, or is close to, "Tiny smile! Yes!"

As best I can recall, that's the thought process (or even spoken words?) of the POV character, pleased that he (?) has provoked a subtle sign of pleasure or amusement from another (male?) character. I think the second character is typically reserved. For example, this could be Zhao Yunlan's POV about Shen Wei. (I usually don't ever read fic for a canon/fandom I don't know, but I've read maybe a couple dozen Guardian fanfics.)

But I can't remember anything clearly! I don't think I made up this interaction entirely, but if I didn't, where am I (poorly) remembering it from?