She didn't know about Yami and Yuugi; they had never told anyone. The two were always close so everyone assumed that they were just friends. But she followed them one day, having grown suspicious when someone asked Yuugi out. Yami had reacted badly, pulling Yuugi away and threatening the unsuspecting person away.
What she witnessed completely turned around the way she saw her two friends. She had followed them to the park, unseen by the two. They disappeared into the trees. She wondered how to get closer without being seen.
Then she heard those words and froze. "I love you."
