Karin, an older sister, lived a poor but happy life with her younger brother. One day, their village was burned down and she was sold to a slave trader. She chose to become a sex slave in exchange for her brother's freedom but... she begins to have unreasonable rough sex with her master... Her virginity is forcibly taken away and she is forced to do things she has never even thought about before. But this is all for her younger brother, right?
I don’t know if the author has explained the group name or not, but in my understanding, "yoko" means "next to", "wanko" means "dog" (in a cute way, derived from onomatopoeia), and "dou" refers to a certain kind of building. So it may be "Yokowanko Dou" or just "Yokowankodou".