An AI only applies to the second character. The selected character's choice is under your control.
Example:
P1 is a Maniac, P2 is a Knight.
Case#1: P1 is selected. You can choose Romantic or Pragmatic for P1. P2 will always be Romantic.
Case#2: P2 is selected. You can choose Romantic or Pragmatic for P2. P1 will always be Pragmatic.