Sakura
Sakura's familiars formed their arms into thin shadow tendrils and swiped at the creatures, attempting to slice a few of them in half. However, they were only able to get in a couple of attacks before the creatures turned and ran, leaving the considerably slower shadow familiars behind them. eanwhile, Sakura, having jumped out of reach, had started to chant.
"Schaffe Bogen!
Lade den Schattenpfeil auf!" she said, her bow appearing in her hands, along with a shadow arrow, with a small sphere of shadow on the tip.
"Aufladen, Aufladen, Aufladen!" she continued, the sphere of shadow gradually growing larger and darker as she chanted.
Then, she pulled back on the bowstring and released, sending the shadow arrow flying towards the enemies. Just as it approached the middle of their formation, she shouted once more.
"Explodieren!"
With that, the sphere on the tip of the arrow exploded, letting out a wave of darkness, corrosive to any spiritual or magical entities in the radius. Hopefully, it would destroy the bulk of the monsters that were chasing after Nanako and the boy.
Shirou
To Shirou's initial surprise, instead of making a charge at the obvious threats, the creatures ran in the opposite direction, obviously following after Nanako. Quickly, however, he realised that they must be targetting the boy. Presumably, they were part of why he needed protection in the first place. Seeing that his close-range defence would not be needed, Shirou desummoned the swords.
"Trace on!" he said, before tracing a bow, waiting a moment to take account of their movements and of Sakura's attack before deciding what to do next.