Major Antagonist

Antagonist is the character in a story who is playing plot-defining role against the protagonist i.e. can be considered his enemy.

This visual novel features one or more antagonists playing a major role in the story and the protagonist trying to overcome them is a crucial part of the plot.

Note that antagonists are not necessarily villains as well. The enemies of a Villainous Protagonist for example can easily be morally good and still be antagonists.