Here is what happened to Rika after the fight between Yuta and Geto:
At the end of Jujutsu Kaisen 0, we saw Rika die and Yuta go away to train with Miguel. But during Yuta's mission to kill Yuji, Rika easily manhandled him which allowed Yuta to deliver the final blow to Yuji.
So, how is that possible? Well, what appears after the Shibuya incident is not the same Rika as the one that appeared in Jujutsu Kaisen 0. In Jujutsu Kaisen 0, Suguru Geto explained that Rika is a sentient spirit of endless cursed energy that can be tapped into at will by Yuta. However, in chapter 178 of the Jujutsu Kaisen manga, it is explained that after the spirit of Rika Orimoto passed on, the vessel called "Rika" becomes Yuta's cursed technique, which can act as a sort of sentient storage. now if you want to know how Yuta kills Yuji the link will be here.

#jujutsukaisen #jujutsukaisen0 #jujutsukaisenmanga #yuta #rika