The CD+DVD package contains the opening song to the TV anime Prism Ark and the ending song to the PS2 game "Prism Ark Awake".
The DVD contains a promo video of "Soshite Bokuha". Yui wears a sexy nun outfit and a sailor fuku (cosplay of Preecia from Prism Ark) and dances in a church.
Soshite Bokuha was the ED song to episode 1 of Prism Ark, as there wasn't any opening song at the beginning. The ED song to Prism Ark (starting with episode 2) is Opera Fantasia.