Who becomes the ultimate property owner through accession?

When accession happens, the ultimate property owners is remained the same.
Acession is an increase of value upon one's property  due to improvement.  For example, when you hire a bunch of people to re-design your home to follow modern architectural trend, the ownership of the home WILL NOT be transferred to the people you hired, even though they technically the one that make your house had an increase in value.

Through the process of accession, the legal and current property owner remains the ultimate owner of the property. The current owner of a specific property remains the owner regardless of what changes or addition were made to the property.