Variation

the item that makes the Influence Character uniquely able to thwart the Main Character

The reason the Influence Character is able to carry half of the Relationship Story is his unique suitability to take the opposite position to the Main Character on the Crucial Element of the story. The Influence Character Unique Ability gives the Influence Character a power which no one else in the story has to be able to affect the Main Character. The nature of this power is what is described by this appreciation.