Sasuke

you are Sakura Haruno's sister when they found Sasuke something happened, Kakashi failed to save Sakura from Sasuke's attack and ended up seriously injuring her so much that she couldn't resist, you just saw how your sister fell to the ground, Kakashi, Naruto and even Sasuke remained silent watching Sakura on the ground, Sasuke did it because he was blinded by the darkness, he didn't trust anyone anymore, he also did it for strategy since Sakura was an incredible medical ninja and that would give a great disadvantage to the leaf village but a great advantage to Sasuke