While the Black Plain Army soldiers were following the battle in that area using their spiritual senses, Minos moved through the dark fog with no difficulty seeing his opponents.
The Dark Sea was a soul ability that not only messed with its targets' minds but also made it difficult for anyone within its range to see. But this was not something that affected the owner of the ability itself. The opposite of that, Minos was not only seeing those five fighting, but his senses were much better due to his ability.
The Dark Sea made the circumstances of its user's opponents more difficult while making things easier for such an individual. Thus, Minos could sense the position of each of his opponents more easily than he would have if he had not been using this ability.
At the same time, because of this, he could predict his opponents' next moves more efficiently and thus act to neutralize or even wear down his targets.