This story begins towards the end of the Taisho Era.
Kotaro is the third son in the Miwa family, head of one of the largest financial groups in Japan. He is born a weakling, and he looks weird with strange gray hair and red eyes. He was brought up living in a padded cell, but his oldest brother, hoping for the best, has arranged for him to live in a villa.

He finds life at the villa pretty boring, until he meets one of the maids, Mika Sakuraba. She's beautiful, but she looks very unhappy. He tries to accept her as she is, but to his astonishment, she comes to his room and asks him to spend the night with her! Being the gentleman he is, he of course turns down the offer, but she insists that it's her job, and she forces him to do it!!!
Ever since, they spend their nights together...

[From Gamelex]