With the intent to broaden videogames’ audiences, and based on the Media Equation study on the law of similarity–attraction, we propose aligning the NPCs’ assertiveness level to the player’s own assertiveness level. We developed a testbed game, a 2D puzzle platformer with a companion NPC, with two versions of the NPC’s behavior, one for each end of the assertiveness scale. We conducted a 2x2, between-subjects experiment (n=48), in which Assertive and Non-Assertive subjects were randomly matched with one of the NPCs. Subjects recognized the NPC’s personality type, giving a significantly higher assertiveness score to the NPC endowed with assertive characteristics. Non-Assertive players reported significantly higher Tension scores when interacting with the Assertive NPC than when interacting with the Non-Assertive NPC. However, based on assertiveness level alignment, there was neither a significant difference in the enjoyment of the experience nor in the player’s affinity for the NPC.