I feel like I'm getting too much credit when Pie did 99.9% of the work. ._.
Anyway, I discovered that both prologues--
PROLOGUE1 - Prologue Part 1 Slow Ver. - Hell's Door (not instance)
PROLOGUE2 - Prologue Part 2 - ??
--play during the, well, prologue that you click through right after you create a new character. The first one plays during the manga-ish parts, and the second one plays during Iris' fight with the monster.