There's 'Yuji and Nobara: Unseen Connections'. This fanfic delves deep into their friendship that could potentially turn into something more. It has some really interesting scenarios where they rely on each other's strengths and learn from their weaknesses.
Itadori did indeed die in the manga. His death had a significant impact on the story and the other characters. It was a turning point that led to many new developments in the plot.