Paleolithic Phenomenon

Levi, a seventeen year old boy forced to grow up early due to him having to raise his 3 year old sister was walking to the convenience store with her when, after a series of events, he finds both himself and his sister in a montane grassland. After a while, he finds out he’s in a time period where there are no rules, and where survival of the fittest truly reigns supreme: the Stone Age. Levi is forced to adapt if he wants to protect both his sister and himself. (For those who absolutely hate sex scenes, I warn you, although most of the story is normal stuff, there are smut moments.)