Legend of Mythical Empress is a quest in Xenoblade Chronicles. It can be received by Gerugu in the Traveller's Rest on Bionis' Leg. If Riki is in the active party, he will comment.
The quest is available after completing With Even More Gratitude and It Definitely Exist!, and once the Colony 6 area affinity reached ☆3.5. The "green" relationship prerequisite between Pachipa and Pipiki is obtained once the Frontier Village's quest It Definitely Exist! has been completed then Pachipa is spoken to before 12:00:
Upon completion of this quest, the Affinity Chart will change: