Disk Vol.8 "Heart to Heart"
From Ephinea PSO Wiki
"Heart 2 heart" was created by Duffy as part of the Japanese Blue Burst servers one year anniversary celebration. Community members were able to submit songs to officially be included in the game. Duffy's submission described the song as, "This is a crappy song made by an amateur, but it'd make me happy if lots of people listened to it".