AereA

All of the sidequests in AereA will be given by the student NPC named Hubert in the music hall. None of them can be missed, and he will simply give you the next one in line as you complete them. If you do all the sidequests for all the areas you have unlocked, you'll need to progress the story and unlock a new area before he'll have any new quests to offer you.

The quests will complete as soon as you fulfill the requirements in the field, so there is no need to return to Hubert to turn them in - you get the rewards right then. However, make sure you go talk to him after completing each quest to get the next one he has. The last sidequest will take place in the lava world.