Im heading over to Japan in late June; and I was curious to know if the pillows are available as choices in the Karaoke bars/rooms. If so, does anyone know what songs they'd have?

At least one place in the nation has hybrid rainbow (albeit only because of mr. children).

Any case, I totally rocked it like 4 or so times (at various occasions) - which lead to the surprising experience of my meeting some cool Japanese ladies who I was randomly (it seemed to me at the time) approached by at a friend of mine's concert, after they recognized me from a picture of me singing during one of the aforementioned karaoke escapades with said friend, who it turned out they where fans of...

Anyway, yes, there is some pillows, but in my (limited) experience, nowhere near enough.

Yes they do. Some places more than others. Depends on the system they use I think, but one place had like 3 choices and another had like 20. Some don't even have 1 (that's a shitty place).

This is semi-off-topic, but I'd love to get my hands on a karaoke version of a couple of pillows songs, including:

One Life
Swanky Street
Monochrome Lovers
Sha-la-la-lla
Our Halley's Comet (TB version)
Hello,...(Instant Show)

But they don't exist