Spoiler Warning. Conjecture abounds.
It think the biggest mystery about Asura is the enigma of his birth. Here we have this creature that is speculated to not even be human. (I mentioned my thoughts on it in my post about Witches.) So with him we are immediately confronted with the realization that this guy’s bad news.
Of course, I think in order to get onto Death’s good side the way he did, all free of suspicion for as long as he was, he would have to be very glib, and charismatic. At least at first. Perhaps he was one of those con artist types with some serious paranoia. Paranoia that just kept growing, and growing until it consumed him.
So he started pulling away from the people closest to him. Perhaps the reason he started wrapping his face in those scarves was to hide the way his body was changing from his increasing madness. I can see him attempting to hide what may have been to him a transformation, but to others would see as a downward spiral. Maybe he would hide because he knew they would think differently than he did about it, or maybe he would hide because he didn’t want them to see his new power, and become jealous/try to take it.
Either way, I think the rise in power made him even more paranoid. That he fell into a Gollum like way of thinking, coveting it, and never wanting anyone else to have it. Thinking that if people knew he had it they’d want to steal it from him.
So his entire quest backfired. His search for power in order to calm his fears made him more afraid which made him seek more power. And so on, and so forth. Which probably lead to him suspecting his own weapon, and eating it. Which I think was the moment he took the first real steps into becoming the Kishin. The steps that allowed him to actually begin devouring human souls, and thus thrust him into becoming the Kishin.
I don’t think he lasted more than a few weeks, maybe a month or two without being outed after that, though. People would have started wondering where Vajra was. They would have started to worry about their missing friend, so they would have found out.
And the outing was probably what lead him to kill the three warriors he killed. And what forced Death to take action. Because I really think Death was forced to take action.
I can’t tell you where Asura’s problems stemmed from. They could be a wide range of things, all of which would come down to mere speculation. Perhaps his mother told him conspiracy theories as bedtime stories. Maybe he grew up somewhere where everyone stabbed each other in the back. Whatever the origin of his problems, I believe that Asura could have been saved if people had tried to understand him better.
Now I’m not saying that Asura is just a misunderstood baby. He fucked up. He’s a bad guy. But everyone has reasons, and there tend to be ways to keep them from going down the wrong path. Most of the time when we’re talking about bad guys, though, it’s the people who didn’t get the help they needed.
Which is why Maka is such a strong force in Chrona’s life.
Note: The direct correlation between insanity and severe physical deformation was brought to my attention by onehundredsouls who’s a serious power on SE info.