>>281581629
Just finished the first volume of this
It has no blood related sister NTR before the story started but the protagonist gets back at the young master that did it by seducing and fucking the young master's sister.
Actually great romance between the protagonist and her if I am being honest. And supposedly in book 2 it gets even better. I am also mostly shitposting about the NTR at the start since it's made pretty clear that the protagonist never saw the girl as anything but his sister