Context
Helltaker is a game by VanRipper. It has a character named Modeus, The Lustful Demon. She is the horniest character of the cast. At the end of the game there is a gag where she says romance is the kinkiest shit ever. She says that while reading a romantic comedy book titled Spider Season. The joke is that despite being a literal sex fiend, she is extremely flustered by the idea of innocent romance because she has never heard of it before. Nothing else is said about the book.
In 2017 VanRipper made a comic titled Mosquito Season, about a guy dealing with annoying insect girls in his house[1]. It features a spider girl. At the end, the protagonist captures one of the mosquito girls that have been harassing him all summer and feeds her to the spider girl, which has a lot of romantic subtext (even though it is done as an act of revenge) because offerings of food like that are courting behavior among some species of spiders. It appears to have been quite popular on DeviantArt and 3 years later on Youtube someone dubbed it[2].
The book Modeus is reading at the end of Helltaker is titled Spider Season - a direct reference to that earlier work of VanRipper and implied to be a sequel where the spider is the focus of the story. VanRipper later posted a short comic on his X (formerly Twitter) where Modeus and The Helltaker watch the movie adaptation of the book[3], featuring the same characters seen on the original comic, thus confirming it is indeed a sequel to that.