They are separate products and the full release will need to be purchased separately.
The prequel was always intended to be a stand-alone experience to gage interest in the characters and the concept, which is why I structured it as a self-contained story with a beginning, middle, and end.
The full release will contain three routes at time of release with two more being added shortly after release. Each route will be around two hours in length, so at launch it will be six times larger than the full game and with all total content it will be ten times larger.