How to get this quest
During the intro, you get this quest after Pleaful Whispers. Skipping the intro will count this quest as failed.
Battling demons
You'll have to fight demons during the quest. Those enemies are actually easy. Using Bite of the Snake followed by Slash of the Tiger is enough. to win. Rose and Richard are also good damage dealers.
Rose versus Richard
During the quest, Rose will briefly become the sole playable character. Go join Richard and Alicia. A battle will ensue. Losing is the only option. After that, some follow the plot and some battles until the final confrontation. Note that this is the only battle of the quest where defeat doesn't lead to a Game Over.
Aura versus Richard
Heal before facing Richard (Aura can use Energy of the Rabbit outside battle. There will be two consecutive fights against Richard. For both battle the following procedure ensures an easy win:
After Aura's victory, the plot will count the quest as failed.