At the end of your training week, Eda gives you a hammer and axe. You can use them to break pebbles, turning them into small stones, and chop twigs, turning them into small lumber. Bring 15 small stones and 15 small lumber to the carpentry shop on a sunny day to upgrade your house for the first time.
Gather Pebbles and Twigs
You can find pebbles and twigs by walking around the mountain paths south of your farm, as well as other paths and forest areas in Oak Tree Town. You will need 15 small stones and 15 small lumber to upgrade your house. More Pebbles and Twigs will appear each day, so be sure to explore until you have found the required number.
Break the Pebbles and Chop the Twigs
After you have 15 pebbles and 15 twigs, you should take them out of your inventory and put them on the ground (choose "Place" to put them on the ground). You can put all of them down at once. For the pebbles, equip your hammer and use it on the pebbles until they turn into small stones. For the twigs, equip your axe and use it on the twigs until they turn into small lumber.
Go to the Carpentry Store
The carpentry store is open from 8AM to 6PM on every day except Sunday. When you have 15 small stones and 15 pieces of small lumber, just go into the carpentry store on a sunny day and there will be an automatic cut scene. Gunther will supervise while you upgrade your house.
Features of your Upgraded House
Gunther has given you a craft table. Check on the side of the table that has blueprints on it if you want to build something from any blueprints that you have. You can get more blueprints from vendors in the Trade Depot. Check the side of the table that has a wooden box on it if you want to rearrange your furniture or change carpets and wallpaper.
In addition, your upgraded house has a closet. You can use the closet to change your outfit, and you can also change your appearance (eye color, hair color, skin color, face style).
Gunther added a barn for livestock. Later, Eda arrives and gives you the cow, Hanako, whom you took care of during your training week. Be sure to go to the general store to buy fodder for your new cow. You can also buy grass seeds and plant them, then use the sickle on the grass (after it becomes tall) to turn it into fodder. After that, just put the fodder into your Storage Box in your house. The fodder from the Storage Bin will automatically come out of the fodder box in the barn.
Now that you have upgraded your house, you can go to the Carpenter's Shop and talk to Corona to see what the next upgrade (Fine Farm House) will require.