Should we include the bishamonten's_pagoda tag? It seems that the personification of the jeweled pagoda is doing stuff to Nazrin in that porno book that Sakuya is reading.
It looks to me like it is a parody of that one pose from Gachimuchi with Billy Herrington and Duncan Mills, which has been parodied before by a number of other works (For an example of this, see post #1799417).