The Stream Treasure Map
Your very first job in the Stream map is from the lady near the well, just
south of the Jizo save shrine. She will request you to catch her a River Trout.
You can find the fish if you follow the west-bank of the stream north,
until you find the fisherman wearing a yellow shirt and purple pants.
To catch a River Trout you can use a regular Bamboo Rod or Carbon Rod. The Trout are a medium-sized shape in the water and they like to snack on Worms, Maggots, Bee Larva, and Fish Eggs. After you catch the fish bring it back to her and she'll give you a Treasure Map.
The map will tell you to go East 30 paces from the Jizo, north 10, west 5. That spot will be directly underneath a tree. Examine underneath the tree and you'll find something buried. Then the errand is over.
Your new rival
As you try to cross the bridge after finding the Treasure Map, you will
be stopped by a junior collage student named Naoko. She is looking for
a rival to challenge her fishing skills and you happen to be the person
she has selected! Naoko will request that you catch the largest Ayu and
bring it back to the bridge. You have as much time as you need to
complete the errand.
To beat Naoko at her game you need to catch an Ayu that is 8 inches or larger. Once you have the fish return to the bridge and talk to her. If you win then she will reward you with the recipe for Salt Grilled Ayu.
Learn how to swim
When you try to go into the water you'll hear a man tell you that you can't
go in unless you know how to swim! To learn the skill you will need to hunt
down Old Smarty, a hermit who lives just north of the bridge where you
challenged Naoko. When you go inside and talked with Smarty he'll wake up
for a brief moment and tell you how to swim.
After the errand has been completed you can now swim through water just by walking through it. Old Smarty will only teach you how to swim if you have the "No Swimming" entry in your Diary. As you level up your character, your swimming technique will increase. The higher your swimming technique, the faster you can swim. When you wade through the water you will loose Hit Points.
Remove the boulder
In the northwest corner of the Stream map you'll find a large boulder. A
man explains that there's a wood god living inside the rock so they
won't destroy it even though it's blocking the path to the next area. He
suggests you go talk to Old Smarty.
Back at Smarty's place, the old man talks about a little shrine near the boulder. If you put an offering into the shrine the boulder might move. Smarty then falls asleep again, so Kayo has to tell you the fish needed is a Yamame.
Catch a Yamame in the area west of the wood god's shrine. The fish needs to be above 12 inches else the little god won't listen to your request. When you put the appropriate sized fish into the shrine the wood god will remove the boulder that leads to the Mountain map.
Find the Bottled Recipe owner
Now that the boulder has been removed, go back and talk to Minoru. He says
that he found a cooking recipe bottled and floating down the stream. When
he cooked the recipe it was delicious! Whoever wrote the recipe would be
a great wife. Minoru will ask you to find the person who put the recipe
into the water. He gives you the bottled message as a clue.
Take the bottle up to the Mountain map. Follow the path until you reach the bridge, but instead of going across the bridge follow the lakeshore to the east. You will find a girl with braids, wearing a brown sweater. Shizu admits to putting the recipe in the bottle and floating it downstream. She did it in an attempt to teach the local fisherman how to cook. They are all very terrible chefs!
Back at the Stream, Minoru tells Shizu that he found her recipe. He then asks if she'll cook for him forever as his wife. Shizu accepts Minoru's proposal. To reward you for your assistance Minoru will give you the recipe for Butter Grilled Big Iwana.
Harvest Sprite happiness
If you swim into the middle of the Stream down near the south side, you
will find a strange fellow. He says he is a Harvest Sprite and he wants
to give you an item that will change shape because of your happiness.
What he says doesn't make much sense! The sprite gives you an item and
then leaves.
After he leaves you discover that the item he gave you was a ??? Seed. In your Diary you'll see that you have completed part 1 of The Straw Millionaire errand.
The Great Duel
Along the path that leads to the Mountain you'll find a girl named Yoko.
She is glad to see you because she has been invited to a duel and she
doesn't want to go! Instead she requests that you go in her place. The
person who started the duel, Takako, is blocking the path to the Field
where you want to go anyway.
Take the invitation to Takako, who is blocking the path to the Field
map. She is disappointed that Yoko was too chicken to come herself.
Takako refuses to move from the path until you bring Yoko to her.
Yoko explains the whole conflict started over some food that she had given to Takako. She thought it would be a good birthday present but it turned out that Takako hated the food! Yoko will help you get her to move if you find out what food Takako likes. After talking with Takako you find out that she likes Salmon.
Catch a Salmon from the Mountain map and give it to Yoko. She will make a meal to give to Takako. Yoko gives it to the grumpy junior and all is forgiven between the two of them. Now you can get to the Field map. Yoko also rewards you with the Boiled Prawn Recipe and the Blackened Newt Recipe. You may have already received the Boiled Prawn Recipe if you had participated in Sachiko's Black Bass Festival back on the Mountain.
This errand will be available after you go through the Mountain and help Naoko catch the Great Brown Trout.
Mamoon the Curry Chef
Down south past the village you'll run into an orange-shirt man who is
blocking the path to the Rapids map. He says he is a curry chef and you
can't get by until the curry is finished. Mamoon then gets the idea to
ask you to collect the rest of his ingredients. The fish he asks for
is an Itou.
The Itou are around the Waterfall in the Stream. Use your washtub to float out to the waterfall, and wedge yourself against the wall so you don't float away. Then just equip a bait rod, a Small Fish, and toss your line into the middle of the Waterfall. Eventually (and with some patience) you will catch the Itou. Take it back to Mamoon and he will request a Cherry Salmon next.
The fish can be found just south of the Waterfall and there's plenty of them. Bring the Cherry Salmon back and Mamoon will request his last fish. He needs a Prawn to complete his curry dish. The Prawns are in the darker water of the northern pond in the Field map. When Mamoon is finished cooking he will unblock the path to the Rapids, and drop the recipe for Raw King Carp.
Stream Cooking Contest
Along the path you'll find a chef and a funny man named Bearnaise. They are
there on a task from their employer, Prince Yuburicho, to find the best
tasting fish dishes.
You can enter the contest and compete against their chef. You will have
5 minutes to catch the necessary fish and cook 2 fish dishes.
The contest is difficult to win if you aren't at a good level of cooking skill. You will most likely win if you are at Decent level. The easiest recipes to use are Salt Grilled Ayu, Goby (Haze) Tempura, and Fried Kajika. All 3 of those fish can be found in the southern waterways of the Stream.
If you win the contest, Bearnaise will invite you to participate in their main contest but you are required to have at least a Pro level of cooking skill or higher before you can participate.