Based on the erotic game by Alice Soft. 
 
Kinosaki Mao lost his mother since middle school, and living with just his father Hajime.
But his father too, suddenly left him at the same time he's enrolled in university.
Leaving only a note that told Mao to not worry about him. 
 
Then 4 years passed, near the end of Mao's graduation, He's still not able to get over his mother's death, and developed Gynophobia disorder as a result. 
 
And then one day.
His father Hajime came back home bringing his new wife.
His new wife Arima Shiori, even more than her beauty, her character too is impeccable, she was an ideal mother indeed.
Bewildered Mao, began to live a sudden life together with a new mother.
Shiori is wrapping Mao with her cheerfulness and kindness. 
 
While coming in contact with her, Mao is gradually attracted to her as a woman rather than as a mother.
The action Shiori takes after becoming aware of that, is......