It takes about half a second for Ritsuka to realize that by 'spooky season' he means Halloween, given that it's still an entire month until October and that was not even something she'd been thinking about yet. When she does make the connection though, there's a very, very brief moment where her expression can only be described as a thousand yard stare, though she almost immediately recovers.

"Oh, yeah, that could be fun! Do you usually do something for Halloween?"

Please tell her there's no idol-wannabe dragons involved.......