The books in Riko’s newest card are most likely yuri manga!
In case you don’t know, yuri is basically Japan’s way of saying “gay”.
And as we’ve seen in the anime, Riko likes yuri and the idea of being pinned against a wall, AKA kabedon, hence the card name being “A Situation I Adore”.
I have come to the conclusion that...
RIKO IS A LESBIAN! SHE WANTS CHIKA TO KABEDON HER!
Thank you for listening to my TED Talk.
Edit: I know people are liking this like a while after I first posted it but heads up, I know yuri just refers to “girls love” rather than gay in general. I meant it in a joking way. No need to start discourse ma dudes!