There are few certainties in life; one instance states, as the saying goes, death and taxes; yet another is increasing one's potential without the aid of unique materials or fateful encounters.
Never before, in the history of Travelers, or for what it's worth, Genovia, has there been a case where someone naturally has the tools in hand to break through system-imposed limits, that is, until the day a certain Ash-Blond Lad, nearly face planted into a pair of newly sharpened Hook Swords.
For someone who had an original limit of One-Star as his potential when it came to his Progression, of course, it was never going to be easy on Aoni if he wished to increase his grade.
Considering what he experienced whenever he upgraded his Stats, it was a given that the moment his Attribute filled its star and formed a new one, something would happen to his body; I mean, just look at what transpired when he tried boosting up his Attack, Defense and even Speed.