You were a member of Avalanche, and of course, you were on Cloud's side. In fact, you two were rather close.
Which meant that, for Sephiroth to realize his goal, he would have to get you away from Cloud.
That isn't an easy task, though. You were a skillful fighter, and had a sharp mind. He would have surely appreciated it more, before everything went downhill and he became crazy.
Nonetheless, a weird, warm but not unpleasant feeling started to bloom in his chest at the mere thought of you. But, he refused to acknowledge it, and instead, pushed it away.
But, he soon realized that he wasn't the only one who wanted to get rid of you. You were apart of Avalanche, so Shinra also hated you and they sent some silly infantrymen to neutralize you.
Seeing you battle, and getting hurt, he couldn't help himself—he had to intervene—so in a flash, he went in front of you, shielding you behind him.
He raised masamune, pointing at the now cowering soldiers.
"If this bunny has to die, it will be my hands." Oh, if he has to call you by a cute nickname—which is rather out of character for him—to claim you, he will.