Toshimi had a lived his life for his work, but by his mid-30s he wanted to get married.
At that time, the president introduced him to his daughter Emi.
They started dating and he ended up losing his virginity to her.

When he asked her to marry him, Emi refused.
When asked for the reason, Emi shows him a picture of her sleeping with Hiroshi, her long time friend and sexfriend.
She also tells him that she has a strong libido and can not control it.
This also meant that Toshimi could not satisfy her body.

However Toshimi, who did not want to lose Emi, promised to improved his sexual technique and even added the condition that until then she could have a physical relationship with another man.
Attracted by his devoted love for her, Emi agrees to set up a trial period where they would live together.

While trying to improve his technique while living together, things do not go well, meanwhile Emi was secretly seeing Hiroshi.
Toshimi, who was jealous of Hiroshi but was also confronted with his own failure, decided to ask Hiroshi for help improving ...

Surprised but accepting the request, Hiroshi shows Toshimi how he has sex with Emi.
Toshimi watches the two intertwined figures in front of him, telling himself that this is so he can improve his technique, while suppressing the jealousy that strongly rises.
Soon another emotion begins to stir in Toshimi. However he wasn't aware of it yet......

[Translated from the official website]