Ryo Tatsumi, an orphan raised by his stepmother Madoka after his parents died in an accident, shared unacted-upon desires with her. This changed when he learned Madoka owed a large debt to the Yotsuya family. To free her, Ryo offered himself into servitude to the family head, Akie Yotsuya.

Entering the Yotsuya mansion expecting work, his duties included intimate acts such as orally cleaning Akie's genitals as part of a daily ritual, during which he had his first sexual experience with her. His role evolved into managing the household while providing ongoing physical services to Akie. Akie's sister Reiko later arrived, immediately took sexual interest in Ryo, and initiated encounters with him. Reiko then facilitated Madoka's move to the mansion, reuniting Ryo with his stepmother.

As the household expanded to include Akie, her maid Fumi, Reiko, and Madoka, Ryo uncovered hidden connections between the women beyond their Yotsuya ties, complicating his relationships. He possesses light brown hair and brown eyes.