Tachibana Ai

Reina's younger sister and Kasumi's bride to be as arranged by their parents, Ai pretends that she detests the idea of marrying Kasumi, but in fact she is really crazy about him.

Ai decides to use her summer vacation to help her sister on the excavation and is initially excited about seeing Kasumi after a gap of ten years, but once they meet they can't seem to keep from fighting with each other.