Tifa is going out with Cloud, but notices that it's nothing compared to what she had with Zack Fair with who Tifa was together with for quite long time. All she can do is remember the times and how it was with Zack. They even were engaged. But one day Zack was put to go on a mission, which he didn't want to do, but had no choice. He went on the mission and swore that it would be his last, so he could be with Tifa after it as much as he wanted. But Zack died on his last day doing his duty. Even though he died and it's been years, Tifa just can't forget about him as her heart still aches for him.
Cloud isn't blind, so he sees through Tifa, but he still loves her, eventhough She loves only Zack in the end.