When Shirou and Sakura fanfiction gets it right, it digs into emotional conflict that the source material only hints at. The narrative often hinges on Shirou's moral rigidity clashing with his compassion, especially after the reveal about Sakura's past and her connection to the Grail War. Is his desire to save everyone compatible with loving someone who might be a 'monster' in his own worldview? Good fics don't let him off easy. They make him grapple with the fact that his ideal, if applied mechanically, could mean erasing the person he loves to 'save' her.
A lot of the best conflict comes from shifting perspectives. We see Sakura constantly battling her own sense of unworthiness, terrified that if Shirou sees her fully—the Matou magic, the Shadow—he'll recoil. The emotional tension isn't just about external threats; it's about two people who love each other but are emotionally speaking different languages. Shirou speaks in actions and ideals, Sakura in endurance and hidden pain. Fics that explore the aftermath of 'Heaven's Feel' are particularly brutal on this front, dealing with recovery, trauma, and whether a relationship built on so much secrecy and sacrifice can actually function in daylight.
What I find compelling is when writers use their domesticity against them. Scenes of them cooking together or cleaning the Emiya household become loaded with unspoken history. A simple question like 'How was your day?' can feel like a landmine. That's where the real emotional conflict lives, not just in the big magical battles, but in the quiet, awful fear that normal happiness is something they don't deserve and can't maintain.