As the game opens, you find yourself fishing at your local pond. Since you're not catching much fish, you pack up your equipment and begin to leave. On your way home you bump into Sasara, a scientist who is always preoccupied with studying something or other. Sasara has come to eat breakfast with you and your sister Yunna, and she's hungry! Sasara has to finish her work though, and will come to your house for breakfast once she's done.
At home, when you go to wake your sleeping sister she doesn't stir. For some reason your constant nudging won't force Yunna to open her eyes. Sasara arrives for breakfast and tries to wake her as well, but even she can't awaken little Yunna. You exit to your house's main room while Sasara tries to figure out why Yunna won't wake up.
After some time, Sasara comes out of the bedroom and says your sister is fine. She explains that she has been investigating the forest because of a story she heard from someone. It is said that spirits live in the forest and mysterious things of legend can occur. Perhaps Yunna was influenced by this and has become affected somehow. It's best to hear the stories from the creatures living in the forest, as the two of you just standing here aren't going to be much help. Sasara is also going to try to find some help from the forest residents, as the might have some sort of clue as to what is going on.
If you ever get tired, return to your house and talk to your sister. Sleeping Yunna is the game's save point.
Sasara hints that she heard a voice in the area you two were in earlier, so follow her out of the house and head towards the Pond area.
When you reach the Pond, Sasara will ask if you know how to fish.
If you tell her you already know (option #2) then you won't have to go through the lengthy fishing tutorial. The tutorial explains how to catch and reel in fish using the DS touch screen. It isn't interactive, so you can only watch the actions that display.
Sasara also explains that she will be waiting at the Pond. If you give her a fish she will exchange it for a Card. The Card will have information about the fish written on it, and they will be her way of cheering you on. Sasara will give you a Card Folder for your collected Cards, which you can access by going into your Menu (press the Start button or tap "Menu" on your touch screen).
In the southeast corner of the Pond is a strange little spirit. The little fellow is hungry so give it a fish that you've caught in the pond's waters. You will need to hand over 3 fish before the spirit is satisfied. The little fellow wants to go with you! The spirit's name is Kuon (or what ever you choose) and to use her power once she's big enough, press the Right Shoulder button and select the bottom option.
Now that you have Kuon you can travel to the MntStrm area. Leave the Pond by exiting from the northwest or southeast entrances and the path to the Mountain Stream will unlock.