pencil and story: Kazusa Shima

The volume is in Japanese, so I can only guess the story.
The protagonists of the story are two sisters (or two friends, it is unclear), who are dragged into a sadomasochistic tour.
At first they are forced to submit by blackmail, one convinced of sacrificing herself for the salvation of the other.
They are tied up and forced to be sexually abused by their new masters, until they have to possess each other.
Cunnilingus, double penetration, anal sex, erotic belts and many ropes, for a highly erotic sequence, which doesn't need translation to be followed.
Simple, censored designs, which however still manage to convey strong sensations.