To anybody who might see this tracklist and think the piano version of "Kokoro" is exclusive to this single, it's not. It's actually "Shion ~Emotion~" with the volume turned up about two decibels compared to the original Digicube Xenosaga OST, phase inverted, and about two seconds longer of (inaudible without turning the volume way up) sustain at the end before going to about three seconds of silence. It's been EQ'd differently too, but it's nothing you'd notice without switching back and forth immediately. It's hard for me to choose a preference, but I'm leaning slightly more towards the OST version. I know that's more detail than anyone cared to know.
Though not really significant, "Pain" and "Kokoro" have different masterings compared to the OSTs.