Basically Reimu using sex to manipulate Marisa, treating intercourse as a reward in exchange for food. She has some vagina constriction techniques that caused Marisa to get infatuated, so the trade worked in the first place.
the title reads "How to make a dried Marisa ~Untold story about the birth of a Deibu~", so I guess it would refer to the Marisa eventually getting drained of paste due to oversexing.