Wait, has "Catulus are more inclined to love girls" ever been a thing said out loud? Damn, would've been a great theme to explore if we didn't have ONLY 5 CHAPTERS LEFT askffgrrv?
The series description on mangadex (which I assume had to come from somewhere) mentions it. Beyond that... I'll have to reread.
Well there is the ending of chapter 17 which goes-
”catulus syndrome is an illness that suddenly causes girls to develope catlike traits, and afterwards, there is a high chance of making girls’ hearts flutter.”
I believe it was also mentioned during an interaction between the main pair at some point.