So let's see if I get JJK's timeline and historical comparisons right.
Anyone come correct me if I'm wrong.
Heian era Japan: basically an era of horror, complete with curses and sorcerers analogous to Sengoku era warlords. . Sure there's strong sorcerers but the overall level of cursed energy flowing about is just nuts. Violence abounds.
-AT SOME POINT during Heian era: Tengen puts up his barriers which don't...eliminate...Japan's swirling cursed energy but basically reduce it considerably. Or contain it? Not really sure here. The net effect of Tengen's barriers essentially was, overall, a pacification of Japan. Less cursed energy, less curses, less sorcerers. You could equate Tengen's influence to the overall effect of the Meiji Restoration & subsequent enacting of the Meiji Constitution which brought Japan essentially into the modern world.
Net effect of Tengen's barriers: analogous to the Sengoku period of Japan ending, suddenly ordinary people become less likely to give birth to curses or become sorcerers themselves. (the analogy here is that ordinary citizens were less likely to become victims of, or combatants in, war).
Flash forward many hundreds of years. While there are still sorcerers running about, they're far and few between. Same with curses. The entire sorcery society's nexus, Jujutsu High, has literally single digit numbers of students enrolled at two different campuses. Essentially you've got modern day Japan: a (mostly) peaceful, unarmed society, still with shadows lurking under the surface but mostly tranquil. Although things are overall more peaceful, just like in the real modern world, the level of "weapons" is still increasing. Domains are less common but have that whole unescapable sure-hit effect. Bloodline abilities have been refined and developed.
For WHATEVER REASON, even with the barriers in place, even with the now peaceful modern society, Japanese people are still putting out cursed energy at a scale that dwarfs the rest of the world Kenjaku's one of them. So it's not that the world is really peaceful, its underlying violence is being suppresed. There are people who don't like "peace" that's actually closer to fragile, enforced tranquility - and Kenjaku's one of them. Kenjaku might even be patterned on Josef Mengele - crazy dark scientist conducting disturbingly immoral experimentation on human life. Mengele would (hopefully) never be able to conduct his crimes in the modern era; so he (Kenjaku) is reverting the world back to one of war.
You also have Sukuna, who represents more than anything the idea of violence itself. His immortality is akin to the concept that the desire for war, for violent power, never dies. Even getting your hands on one of Sukuna's fingers makes you incredibly powerful, right? Kind of like handing a gun, this super rare forbidden object in Japan, to a violent criminal would increase their threat considerably.
And now, by absorbing Tengen and conducting the culling game, what Kenjaku's doing seems to be two things at once: He's returning Japan to the Warring State (Heian) era by reincarnating old warriors and warlords, and using cursed objects and manipulation of the brains of latent sorcerers to give birth, overnight, to a new generation of combatants. AND: he's using his scientific knowledge gained over many lifespans to take advantage of the chaos and advance the science of cursed energy all at once.
ww2.readjujutsukaisen.com
(If you are not already reading it, that is)
