Asuna's favorite memory had always been the summer when she and Kazuto were seven. Their families were close friends, so she and Kazuto were often around each other, but only briefly. For one month every summer, Kazuto stayed with her family while his parents took a business trip. During that month, he and Asuna spent as much time together as they possibly could. They were perfect companions, and had immediately become best friends when they first met.
Asuna often reminisced about this summer because it was the beginning of her first love. One day, while the pair was playing in the sandbox, Kazuto turned to Asuna and asked her if they were going to get married when they got older. Asuna gleefully confirmed it, and they made a promise to love each other forever. Asuna clearly remembered the joy she felt when she and Kazuto intertwined their smallest fingers in a silent vow.
Nine years later, Asuna and Kazuto were deeply in love and so far, neither one of them had loved another. They had kept true to their promise, and they were both excited at the thought of having one true lover in all of their life; getting it right the first time, so to speak. Many were extremely jealous of the bond the two shared, and they were proud to be that couple everyone was envious of.