You are Ouji Kamogawa, age 19, a bright student with a bright future. However, your dreams of going to a top-ranked university suddenly come crashing down when you fail your entrance exams -- and lose your beloved Yukari at the same time. Now six months later, you're wandering a lonely beach, bitter about all that you've lost.
Suddenly, you hear a sweet voice, crying out for help. It's a beautiful girl -- a young maid -- about to be subjected to a terrible fate at the hands of a band of hoodlums. Thinking fast, you are able to save her virtue.
"My name is Mari," she says, through her tears. "I work as a maid at a nearby mansion. Please...let me repay your kindness."
She takes you to the house she works at, Sea Dragon Mansion. There you encounter her two sisters: the proud and capable Hina and the delightfully cute Mayu-chan. You also meet the mysterious mistress of the mansion, Hime, and the cold trainer-of-maids, Aya.
Welcomed as a guest, you choose to stay for a time in Sea Dragon Mansion. Aya coldly explains the rules of the house: you are the guest, and that means that the three maids will strive for your every pleasure. Ring one of the three bells to call any one of the three maids, and you can use them any way you like.
[From Peach Princess]