She was eating a superglue coated apple, theyr hands are now forever stuck together. Since shes a sly fox she will definitely do this with theyr genitals in the future I have no doubts.
I would love for a Yamada POV chapter so we can finally hear what she thinks about herself or of her relationship with Ichikawa. I know that she is know for voicing her thoughts, but I would love to hear her internal monologue.