It’s sorta weird how the manga improves the plot compared to the novel. In the WN, Staff and Caliper almost immediately get into a fellatio battle before segueing into sex.
Also, I think the final line of the WN chapter this corresponds to says it all
This girl has a very erotic body. Not many girls have it. And I can say that many men like it. Not for me though for my last been decreasing each year. I want to be young again.