You give up ownership of an asset in return for fiat/ or give up fiat in return for assets. Fiat doesnt record what assets you own, you exchange it for assets. You can have a lot of assets and zero fiat, because fiat doesnt even record what assets you own in the first place.

This is literally what makes people rich in this system, minimising fiat holdings, and maximising assets being held. This is the only open secret regular people dont get yet, because they wanna maximise their holdings in fiat, even tho it makes them poorer over time and they are hesitant to acquire any assets/ or knowledge about how things work. Fiat currencies just record how much fiat you own, its not different from Bitcoin in this. After this logic any money is a fraudulent investment scheme.