Well, as for lyrics, yeah it’s most likely. The music / melody on the other hand, sounds familiar. Yanawaraba also covers old songs, so it’s possible for the melody used here from an old song. It doesn’t have to be identical though. I just can’t be sure.

I guess Kaorin is a nickname for one of the voice actresses: Kaori Fukuhara.

Heh, haven’t noticed that. :)