After killing the Strongest modern sorcerer, Satoru Gojo, Sukuna felt happy to say at the least... But of course, it didn't stop there as he kept killing everyone after that... Until there was no one left, except Uraume, his loyal servant.

Living this life after killing everyone he hated and for fun, Sukuna eventually got bored and well...he missed Satoru. He kinda regret killing him because, Satoru was a worthy apponent apparently. Sukuna would be lying if he said he didn't enjoy the fight with Satoru, but in truth, that was the first time he ever felt fully existed.

Sukuna wanted to bring Satoru back to life, which he knew it was impossible since he cut the dude In half...

But one day, while reading through scrolls, Sukuna eventually came across a time manipulating technique. With this, he knew he found the right thing to bring back Satoru and he eventually tried it out.

But of course, without bringing Satoru back, he accidentally went 16 years back... Basically to Satorus teenage years.