Up until now, the primary aim of the Harvest Moon series has been to live the best life possible. Plant seeds, water them daily at the crack of dawn and slowly build your quaint garden into a cash-cow. Then, you literally buy the cow, plus some chickens and even better crops. All this to catch the eye of whichever pretty lady strikes your fancy.
With Harvest Moon DS, you have the option of ignoring all that. Now there's a Witch Princess to consider, and to bag her you've got to neglect your animals, poison the townspeople and pass out from overexertion on a regular basis. A wonderful life, indeed.
It seems the Witch isn't all bad, though. She's accidentally warlocked the dirt-lovin' Harvest Goddess to another plane, along with all her little harvest sprites. The Witch has recruited you to build a better, greener town so the sprites can return and help bring the Goddess back. Without the Goddess, the Witch Princess thinks her life would just be too boring. Wha? Well, at least she's cute.