Well, to understand 'Prey on the Master' manhwa, first, familiarize yourself with the setting and the main characters. Also, notice the themes and the way the story progresses. It'll all come together as you keep reading.
It could be a story or a piece of fictional work related to Saturday. Maybe it's a book, a short story, or even a movie script that has some connection to Saturday, like the events in the fiction taking place on a Saturday.
Adventure is a common theme. Given their nature of going on all kinds of Saturday adventures in the original concept, fanfictions often continue this trend. They might be exploring new places or facing new monsters together.
Archive of Our Own (AO3) is also a great source. Some fanfictions there might focus on the development of their relationship over time. Maybe there are stories where they start as just friends on their Saturday adventures and then slowly realize they have deeper feelings for each other. It really depends on the creativity of the authors.
A 'Saturday Night Novel' could be a novel that is typically associated with being a good read for a Saturday night. Maybe it's a thrilling, exciting, or relaxing story that you can enjoy during your Saturday night leisure time.
It's about a powerful master who finds themselves in the unexpected situation of waking up as a concubine. The story likely follows their journey to adapt and navigate this new role.