The first optional download content pack for Harvest Moon: One World unlocked on March 2, 2021. This bonus pack introduced five optional house interiors and a new level of farm tool upgrades.
The magnificent Doc Jr. has the skills required to upgrade the farm house and remodel its wallpaper, rug, and flooring; the furniture style does not change. These special interiors will be available at his Doc's Inventions shop after downloading the DLC. The five styles are compatible with any size of house you have on your farm.
Farm Interior - 1 Cashmere, 1 Diamond, and 10,000 G
Castle Interior - 1 Sheep Wool, 1 Agate, and 10,000 G
Steampunk Interior - 1 Sheep Wool, 1 Crystal, and 10,000 G
Spaceship Interior - 1 Valais Blacknose Sheep Wool, 1 Sapphire, and 10,000 G
Starlight Interior - 1 Valais Blacknose Sheep Wool, 1 Garnet, and 10,000 G
Remodeling your house will change the current interior, but it doesn't unlock the option indefinitely. If you want to change to another style, you'll need to bring the materials and fee to Doc Jr, even if you have already remodeled to that style once before.
Thanks Shell.Bell__ for the interior house pictures!
Harvest Goddess Tools
Talking to Dva by the mine close to Halo Halo will unlock tool upgrade recipes. These tool upgrade recipes can be crafted at the farm house workbench. After completing the Ultimate tool upgrades, and you have this DLC added to your game, Dva will mention one last set of tool upgrades: the Harvest Goddess tools.
The Farming Tools and the Harvest Tools each require 5 Platinum to construct. The Farming Tools (hoe and watering can) will expand the tools' reach to a 5x5 area. The Harvesting Tools (hammer, axe, and fishing pole) will make it easier to complete harvesting tasks.
Platinum Ore can be found in the Lebkuchen mine starting on floor 13. It can also be found on all floors of the Wagashi mine, which unlocks with the Far East Adventure Pack DLC. Take the ore to Doc Jr and he'll process it into usable Platinum.