Shion's main theme in Episode I is the ending song "Kokoro"(heart) performed by Joanne Hogg. The tracks "Shion's Crisis", "Shion ~Memories of the Past~" and "Shion ~Emotion~" were also written for scenes focusing on her. "Fighting KOS-MOS" plays during a scene that showcases KOS-MOS' power, but composer Yasunori Mitsuda chose to write the track from Shion's perspective for a twist. "Shion ~Emotion~" was first released on the "Kokoro" maxi-single as "Kokoro Piano Version", but Mitsuda changed the track's title in the Xenosaga Original Soundtrack as it fitted Shion best.