Forbidden Phrase

Shizuka had just lost her only parent, her mother, due to a car accident. A young man, Yuuichi, rushed to the hospital and declared that he's Shizuka's step-father. That was their first encounter. The two started to live together, yet Shizuka realized that she was seeing Yuuichi as a man instead of as a father. And Yuuichi was too... in order to prevent the forbidden relationship, Yuuichi decides to leave home, and...!?