The MC in the original release was made without an adaptable 3D model so they needed to remake it in order to better create new content. The prequel gameplay is essentially a parallel story that will connect back into to main game in the future. It was released in order to keep production on the game while the new MC model was being finished.
The new model for the MC of the main game is done now, so they're just updating the original content with the new look and replacing the placeholder anime portraits with custom models for the game.
All the stuff that you liked about the original is still going to be there, the game just lets you now choose if you want to play the main story or the prequel story when you first start. Regardless of which one you choose, there is already a mechanic within the game to swap back and forth between the two stories. Players can also choose to entirely skip one of them if they're only interested in one of the stories.
