So I have a theory about the last page. She seemed shocked after grabbing his penpen, why is that? First, we have to keep in mind that this guy has an onee-san fetish. He does not like lolis, which is why he did not have lewd thoughts about her unlike the onee-san beside her, and is why he's acting with indifference with her. He's probably in a flaccid state, yet the size is still huge. This is probably why she was shocked in the last panel, realizing that the cobra she's grabbing can potentially grow double or triple in size.