From where you started, follow the path to the west till you see a small village, which is in fact "Kerhn" and your destination.
Before entering, however, I recommend you to level up to at least level 5, and at least have 50p on both Yusis and Cynthia's weapons to learn their respective 2nd skills.
Meeting the Villagers
When you first enter Kerhn, some of the villagers come out to meet the "Savior." After the scene, you can take a stroll around the village.
Head to the northwest of the village, and behind the house there is a treasure chest containing "Intelligence Bottle."
I recommend to go to the Item Shop and stock up on Heal and Mana Chocolate. Also be sure to take Antidote Herb and Insulated Stone with you since it will help quite a bit afterwards.
After you have done strolling, head towards the southeast house for a scene. After the scene, head to Cynthia's house, which is at the northeast of the village, for supper and a scene with Cynthia’s foster parents, Hial and Aretti (and some other characters.)
After Yusis wakes up, go west into the lounge and head south to exit the house for a scene with a little girl.
After the scene, before exiting the village, enter the southwest house (which is surrounded by merchants) and talk to the Lunarl Woman, Klesta there for your first Sub Quest.
Sub Quest # 01 : Spice Dilemma
The Tarmeg Seed is east from the Village, near a tree. It’s quite easy to spot it since it shines quite brightly. Take the item (It’s a Key Item) to Klesta to complete the quest.
Reward: Heal Soup.
After the Sub Quest, to reach “Cave of Solum” exit the village and head north, then east and then south, then enter the small grey cave.