It depicts two possible futures.
One where the female protagonist goes steady with Aki and another where she goes steady with Yuuki

[Aki Route]
The day after he thrusts his desires upon Mei, Mei abruptly calls out to him.
There is something she has been meaning to tell him for a while.
Mei says this and, expecting her to say farewell to him, Aki tries to tie her up again.
But what Mei says is unexpected, and with that a change comes to their clumsy relationship...

• Sexual content tendency: Coercion / non-con, requited feelings.

[Yuuki Route]
Since the day he violated Mei, Yuuki has been tormented by guilt. Nonetheless, he expresses his feelings for her. Mei refuses, saying that she is not someone that can choose Yuuki.
However, saying that he will make Mei fall in love with him one day, he attempts to deepen their relationship day by day.
One day, while the two are out together, something happens that changes their relationship...

• Sexual content tendency: Requited feelings.

There is a TL and R18 version.