After you learn of the Ninja Village from someone in the Ary pub, you make your way there.
Learn of the Ninja Village
If you haven't already done so, make sure to go to Ary (the city on the continent that is always dark) and talk to the woman who is talking to the soldier in the pub. She is behind a plant. She will mention the Ninja Village.
Reach the Elven Village
To reach the Ninja Village, you must first go to the Elves' Haven. To get there, go to the lake of Ymir, which is north of Ary. From the guard at the entrance of Ymir Forest, go north and then east across the bridge, then go north and follow the path until it splits. When it splits, go north until you can't go farther north, then go west until you can't go farther west, then go north to the next area.
Go west from the save point and follow the path to the next area. Keep going west, then when the path splits in four directions, go north into town.
Go into the weapon store and pay 20,000 gold to have them fix Chester's bow. Spend the night at the inn. You will receive a Star Broom.
Buy a Dark Robe at the item shop from the shopkeeper on the left. Be sure to buy Rememdy Bottles and any other medicine that you need from the shopkeeper on the right.
Talk to the bow shop owner to get the Elven Bow for Chester, then go north from the food shop to reach Treant's forest.
Have Klarth/Claus ready to summon spirits, and equip him with a Mystical Rune. Equip Cless/Cress and Chester with a Flame Mantle, Mint with a Princess Cape, and Klarth/Claus with his Garnet Ring.
Go north three times, west three times, and north three times. Talk to the girl.
After the cutscene, equip Arche with the Dark Robe and Star Broom, and equip Cless/Cress with the Muramasa.
Go to the left side of this house and buy the painting from the guy who has three dots over his head.
If you want to buy any food from the food shop here, buy Butter. It is the most cost-effective of all the foods that they sell here.
Leave town by the east exit and go east to find a chest that contains the spell Flare Tornado. Then go back into town. This time, use the west exit, follow the path, and go south to find a chest that contains a Blue Crystal Rod. Equip Mint with it right away. Then go back into town.
The enemies in this part of the forest provide a lot of money and experience. If you want to level up here, equip everyone with fire-protecting equipment.
It is recommended to reach at least level 50, if not 60, before proceeding.
When you are ready to leave, use the south exit of the Ninja Village, and choose to go to the entrance of Ymir Forest.
Your next destination is Freezekill, which is southeast from the Ninja Village.