So three... Theories? Questions? Thoughts?
First, is that it was Hino's convoluted way of answering Koguma's question. Because Koguma (I assume second-guessing her own question) says that she had to be imagining things when she asked if Hino tried to kiss her. So Hino kisses Koguma (on the cheek) and says she imagined it, admitting to it.
The second is that it was just a weird way of saying "I'm not ready to fully dip my feet into this pool" by Hino. As in not ready to advance their relationship.
Third, the usual, is that it means nothing and was just meant to be a cute scene between two cute dolts.
Whatever it is, I wonder if we're just going back to the usual school shenanigans, since this was supposed to be the "last event" of the summer break.