Why is Sasagawa Kyoko called Small Class?

I want to explain upstairs-Kyoko in the future article 10+ doesn't have the pronunciation of sauce when he calls Xiaogang, okay?

Probably because ten years ago, Kyoko was called Gangjun-but ten years later, it became something ... which means I don't know how to spell the sound behind = = Actually, I think it should mean Gangjun-but after seeing Gang Ji's reaction, I think it should be a more cordial name-

I don't think it's a couple, because Koharu insisted on saving her after ten years, which means that Koharu still likes Oka after ten years-but as a good friend of Keiko, if Keiko had a relationship with Oka, she wouldn't say so = =!

Well, that's my explanation-in short, good friends shouldn't be lovers.

So I hope to use =v=