Miki Koshikawa is an ordinary high school student who's life is turned upside down. Her Parents divorce and switch partners with a couple they met in Hawaii, the Matsuura's. They have a son named Yuu who is close to her age. The new blended family moves into a large house together. That night her mother gives her a warning.
This is definitely one of my favorites of older shojo. The story is kind of complicated with the many side plots, but it turns out to be a fun roller coaster ride of love and determination.