Originally Posted by ImpactBreaker

According to masa ayu made this song for her mother. 2 X because you use X in math as something "unknown", so ayu wanted to hide who was this song actually for, the first and second X are the name and family name. If you watch the CMs they always say only "A Song for......" and leave the rest blank, making it clear it's a song for "someone that can't be mentioned". To know why the song is for her mother you have to read the lyrics and read masa's article about the A Song for XX album in his website
( http://homepage2.nifty.com/morimasa/ayu.html )