After the end of the culling games, Gojo being free'd from the Prison realm, the death of Yuki Tsukumo at the hands of Kenjaku, along with Sukuna forcibly possesed Megumi by swapping vessels with Yuji.

The sorcerers and the ancient sorcerers that joined them; Kashimo (forcibly) and Angel/Hana. They all had a month to train up for preparations to a big battle coming up

The plan to defeat Sukuna and free Megumi, finally ending Sukuna's rampage in the modern day