From Shoujo-Manga.com:

If you have seen that Disney movie with Jodie Foster in it, ‘Freaky Friday’ (or even the recent version with Lindsey Lohan) then you can probably follow the plot of this manga easily because it is based on the same premise- a mother and daughter (who do NOT get along well) argue and fall down the stairs at their house together, and when they wake up at the bottom of the staircase they discover that their minds have switched bodies! Now 14 year old school girl Saori is in the body of her mother, 35 year old actress Mizuho, and Mizuho is now in the body of her schoolgirl daughter. OH NO! What to do!? There is the struggle of adjusting to the strange situation, followed by the decision to try to keep the news of their switch from Saori’s papa (Mizoho’s husband), and then the attempt by each of them to live the life that goes with their body.