Board Thread:General Discussion/@comment-6986530-20170321154902/@comment-32741767-20171008063827

I'm here. The source for it, was a chinese man in tieba.baidu; While making analysis for the names of the cast he threw this info for Yuka. I couldn't find the exactly words he used but certainly in the Edo period we had something.

Also i don't know his source but I believe him, since hes analysis was a serious analysis.