Promises
A promise is a strange thing. Some people make them without thinking and then regret it for a long time. Others make them and intend to keep them, whether by choice or because they were forced into them. Cloud was that kind of person. He believed that promises should be kept regardless of what made the promise happen. So when Tifa was in trouble, he would rescue her. Just as he promised. It didn't matter that it had taken her three requests before he had finally gave in and agreed. All that mattered was that he had promised her.
And when Aerith asked him to be her bodyguard the day he fell into her Church, he accepted. It didn't matter that it had taken just one request before he agreed. All that mattered was that he promised he would protect her.
And he kept his promise.
He rescued her from the ShinRa Headquarters, he leapt in front of her in battles. He kept his promise.
And it was months later before he suddenly realised that he had never promised her anything in the first place. Everything he had done to protect her had been out of free will. If he had wanted to, he could have left her to fend for herself whenever he pleased. But he didn't. And Cloud knew why.
It was because Aerith only had to look at him with those beautiful expressive eyes and before she even opened her mouth to request anything, his heart would already be saying yes.
I noticed the other day how Tifa asked Cloud three times to promise her before he agreed and then Aerith is just like "Will you be my bodyguard?" and Cloud nods instantly in reply to the date. Score! lol
Disclaimer: I don't own Cloud Aerith or Tifa - SquareEnix do.