Series of images by NM_(tshell2761). It follows the relationship of a man and his sadistic girlfriend in various scenarios involving femdom and bdsm.
Titled Sな彼女 on Pixiv. Accompanied by commentary.
The setting behind these images can be read in the commentary for post #1335122.
The series was later made into a visual novel titled Escalation!, in which multiple images and their scenarios were adopted into chapters of the novel.
