One day during the summer holidays, while all the other dorm residents headed back to their family's homes, the members of the Takamura class were enjoying the remainder of their holiday to the max at the academy.
During this time, Momiji realises that there just happens to be a day where everyone else is out of the dorm apart from her. Thinking that she could have Iori all to herself, without having to worry about the gazes of the others, she barged into Iori's room.

There's just over 24 hours left!
Momiji's many delusions finally explode!
And so their sweet lovey-dovey flirty-flirty day begins.

[Translated from the official page]