Adachi and Shimamura, light novel Vol. 01

Adachi is skipping class when she first meets fellow truant Shimamura in the gym loft, and just like that, a friendship is born. Except now Adachi's having dreams about kissing her, and she doesn't know what that means, but she's pretty sure it's not something you do with a friend. What are these strange feelings she has when she thinks of Shimamura? And is it possible Shimamura feels the same way?