There are two groups of characters in Mystic Valley; the human characters and the native magical creatures that live in the valley. All of the residents will help you in some way to catch the River King, whether it is by giving advice or assisting with completing tasks.
Your little sister has been stricken with a mysterious sleeping ailment. She will be in her bedroom the entire time.
If you bring this research scientist specimens you pick up in your travels, she will reward you with collectable cards. Sasara is in the Pond area anytime of day.
This mysterious traveler will exchange your cards for spending points, and offers a variety of fishing equipment and food items. He is always available in the Pond area.
She was separated from her own brother when you first meet her in the Rapids, but with your help the siblings are reunited. Ahaya tends to get scared very easily, even if her brother is around to protect her.
You will first meet your self-declared "rival" in the Rapids area, and from there he will travel to various areas of the valley. He only appears during the afternoon, and he waits for you to arrive in order to challenge you to a fishing tournament.
He too is searching for the River King, but agrees to help you out with any information he can find about the elusive fish. Ren looks intimidating but he worries about his own sister, Ahaya, and won't hesitate to be a tough competitor during Manato's fishing contests.
The little gang of cauldron-wearing kids appear in various areas and offer advice about the fishing environment they're in. They only appear during the daylight hours.
Just like the boys, these girls can be seen during the afternoon time in various areas of the valley. They just give tidbits of advice here and there.
The river beast won't be swimming in the Mountain Stream until after Tenma joins your party. He will help you reach the next fishing area if you can find a cucumber for him.
Mystic Valley has lots of weird little oddities, and Kodama knows all about them. The talking tree will guide you through your journey to catch the River King.
He is too busy washing his precious adzuki beans to pay much attention to you, but if you ask the goblin may let you wash the beans for him. He can be found in the Waterfall area in the morning and evening hours.
The 3-tailed cat is full of mischief, and appreciates a guy who comes bearing gifts. When Neko becomes happy she'll reward you with a little dance. You can always find her on the far western bank of the Stream, across the bridge of rocks.
This little kid in the Swamp is incredibly hungry! Give him a few fish to become his friend. He really only wants to become friends with Nekomata, but the cat doesn't seem to want anything to do with him. You can find Ogre Child during the morning and night times.
He might be wielding a sharp sickle, but his only goal is to cut away the obnoxious weeds that are bothering his flowers. You can play a mini game with him in the Upstream Waterfall area, and he will help you out in the Waterfall area as well.
The giant wall will block your access to the Underground Lake until you and Ogre Child figure out a way to awaken it. Who would have ever thought that walls could talk?
A creature with a horrible singing voice, Nue will help you out with the very last step you need in order to catch the River King. She wants to see you awaken your little sister.