On page 7 when Itsuki says, "Today's full moon is really pretty, don't you think?" and then he had kind of a stunned expression, then tells her she needs to study more, is something that doesn't translate too well without context. Basically, without realizing it, she told Futarou that she loves him.
Because the Japanese traditionally shied away from direct declarations of love, (and because Japanese in general is often indirect) they would use poetic language to say how they felt.
One of the ways the Japanese would say "I love you" is with the phrase "The moon is beautiful, isn't it?" to their love interest, under a moonlit sky. It would be common in a love letter (for example, see Violet Evergarden, the episode where she helps a princess write letters to a prince) to, rather than declare one's feelings directly, to work in allusions to flowers and the moon.
Futarou immediately understands what that phrase means, thus the shocked expression. But Itsuki is really bad at Japanese, so she didn't understand that she just told him "I love you".
It would have been nice to see a translator's note on this page, because this kind of thing is pretty easy to lose in translation, and I think is a really important moment for the chapter. But now you know! I am sure that Futarou's heart skipped a few beats at that moment, and even if Itsuki didn't understand what she said to him, it might have left an impact. I also wonder if at some point she'll come across this knowledge in her studies, and then realize what she told him that night.