Didn't Kettaro cover the song "From Y to Y?" It's not on his page but I could have sworn I got the link long ago from his list of covered songs. Unless I'm mistaken...
Indeed, he covered it.
If you have a Nico Nico Douga account, you can watch it here.
If not, you can watch it on Nicoviewer.
I guess we should add it to the page, thanks for pointing out :3
What do you think?