By interacting with objects in MYSEKAI harvesting areas, you can obtain the materials you need to build furniture and tools.
When you get close to harvestable items, an action button will appear.
If an object can be harvested from multiple times, you can hold down the action button to continuously harvest.
Go to harvesting areas by tapping the globe icon on the top-left of the MYSEKAI screen.
Harvesting rewards you with not only building materials, but also Show Points, Event Points, Event Tokens and Player Rank experience points.