Speed-running romcom tropes I see, next chapter will have Shion or Mone walk in on them in an awkward position after they were trapped for a bit in there.
Shion didn't explain the significance of the bell, and treated it as a rejection when Itsuki said he didn't want to ring it, even though she didn't actually confess.
When she said "I like you", she made it a hypothetical, then covered it up as just being a weird question to not mean anything.
Itsuki isn't the sharpest, but Shion isn't being clear.