KYAN Chiaki's surname looked made-up to me the first time I saw it. It's spelled 喜屋武, "ki-ya-mu", which sound change would indeed eventually grind down to "kyan" or even theoretically "kyō"... but come on. Kyan?

Turns out I was as wrong. Ethnocentrically wrong. I don't know if it's her real surname, but it's definitely a real surname -- from Okinawa. Word on the street is that it's the 45th most common surname there, and the 2820th nationwide (88% of 喜屋武s live in Okinawa). Karate master KYAN Chōtoku was another famous 喜屋武.

He was also alive long enough ago to have fallen victim to Chan/Kyan confusion. Y'see, the sound in Okinawan that corresponds to Japanese /ky/ is /ty/ (e.g. kyaku ⇔ chaku), and sure enough this name used to be pronounced "Chan" too. Implementing a nationwide standard Japanese was a major goal of the Meiji government, and that included the "normalization" of Okinawan place names. And so, by 1903, the official pronunciation of the village 喜屋武 had already been changed from "Chan" to "Kyan". Later, in 1937, a law was passed making mainland pronunciations for Okinawan surnames compulsory, and 喜屋武 was apparently changed all the way to "Kiyatake" in some cases. (/take/ is another standard SJ pronunciation of the final kanji, 武).

And there are the usual slight variants: Google confirms Kyatake, Kiyan, and Kiyabu, to list just three.

Summary: Chiaki's surname is real, and it's spectacular.