The Heart of the Matter

Details
Assist the Manustery in the creation of Cardians. You must go to the southeastern magic tower of the Horutoto Ruins in East Sarutabaruta, and energize the Mana Orbs that serve as the hearts of the Cardians. Inquire at the Manustery first for details.

Walkthrough
After talking to the guard, go to the Manustery in Windurst Woods and talk to Apururu. He sends you to Outer Horutoto Ruins

Outer Horutoto is located around the west area of East Sarubaruta.

Once you get there, examine the six Magical Gizmo there. After examining all of them, go to the Door of the Magical Gizmo and get a cut scene. After that, examine the six gizmos once again and get out. You will be greeted by cards once you're out.

after the Cut scene, go back and talk to Apururu in Manustery to finish the mission.