Due to suffering from agnosia, Experiment Number 6 had no awareness of his own self or anything else, resulting in a distinct lack of a personality. However, it is because of this that his caretaker, All For One, saw potential in being able to mold him into whatever form they desire, thus leading All For One to nurture him until he developed a distinct one.

In general, Number 6 had a confident and self-assured attitude, keeping calm in any situation, even when he was confronted with a gun. He preferred to avoid confrontation at all times, choosing to flee rather than fight, but he had no problem with using violence when the situation called for it. He also had no qualms with endangering the lives of innocent people as a distraction or for his investigations with the Next-Level Villains.

Despite this, when Number 6 used his skills for disguise and infiltration, he was perfectly capable of acting as a totally different person, being able to hide his true colors and intentions while deceiving others. For example, when he was "Rokuro Nomura", he acted as the clumsy but well-meaning and polite Marukane Performers' manager, without anyone suspecting that there was anything weird about him.[20] As Rokuro’s Pro Hero persona "Rock" he acted as an inexperienced yet dutiful, clever and friendly hero, being able to perfectly blend in and assist Compass Kid with patrolling and evacuating citizens, avoiding any suspicion until he was exposed by the latter hero's Quirk. He could even switch between these personas on the fly, as well as meld them together so “Rokuro” and “Rock” appeared more like the same person, all the while keeping his true villainous nature hidden underneath.