"I'm not talking about the simple, obvious notion that powerful jujutsu sorcerers are prone to extremes when using cursed energy. In fact, even that idea is wrong.
"The correct answer is the soul.
"Some souls are simply more prone to negative emotions—anger, sorrow, fear, irritability, or jealousy. You can't tell when they're young, but as the soul grows, a person's thoughts increasingly drift in darker directions. That is the most basic instinct of becoming a jujutsu sorcerer.
"Just think about it. If jujutsu sorcerers were born entirely through genetic inheritance, then how did the first sorcerers come into being? Suguru Geto, a special-grade sorcerer, had genuine ordinary people for parents. So how was he born?
"It all comes from mutations of the soul."
Yuki Tsukumo watched the waves in the canal, her voice tinged with reminiscence.
"When I first noticed it, I was stunned too. There had always been plenty of evidence, but few people studied it. And even those who did were unwilling to admit it.
"The soul carries human cognition and memories.
"That is why every soul summoned back can clearly remember who it is. And once it enters a body, it can even use its technique. That is because a soul alters the body when it invades it; its cursed energy residue becomes identical to that of the deceased soul, and its technique is engraved upon the flesh as well.
"I even suspect that, if the technique is suitable, the soul itself can use cursed energy.
"So, do you understand now? Jujutsu sorcerers are born crazy!
"This distortion comes from the soul. No jujutsu sorcerer can escape it.
"You think sorcerers like us are normal only because there are even crazier ones keeping us in check.
"You should see how terrifying the past was before Satoru Gojo