Well first of all, we need to go to a place which is north of the town. Right at the west end of the map, you'll see a frog king with wings. To defeat this guy, it is advised that you have a big party. (Recommended to have magic or at least good evasion) To defeat this frog boss, you need to plan it all out since he does hit hard for our level.

After you defeat him, he'll give you green powder. You'll see this in your inventory. Head back to the town square, make sure you are level 15 and then talk to this guy (234,216)

He'll give you the flying sword, in the one of the icon tabs you'll see it as the 2nd icon on the 2nd row:

Then drag your item, place it into the slot that converts it into a flying item.

You can only land in a place with a ring and it has blue stars coming out and land there.

exit north from Choyo Town.
Talk to the frog NPC (X250，Y274).
Do the quest alone or if you have a party, make sure you?re the leader and your party members are with you.
Defeat him.

After getting domo gold a powder from the defeated king, return to Choyo Town. Talk to this NPC (234,216)

You get lv 1 flying skill

Part II

Talk to this NPC again (234,216), gets domo gold lv 5 flying skill
Search for the flying fairy in town. She flies around the town.
once you talked to her, return to the NPC (234,216) again, gets lv 10 flying skill