The story doesn't start off too complex. The main character is a former member os the hero clan and his two addoptive sisters are from the demon clan. The main character wants to protect his family, and so they enter something called a Master-Slave Contract in order to gain the strenght to fight against their enemies.
That's basically what you need to know before starting.
The first thing to note, if you came from the anime, is that a lot of scenes (especially from season 2) were censored. And I'm not saying that the violence was censored, I'm saying that the more lewd parts of the story were censored, so it might be worth going from the beginning with this one.
For the most part, the story develops nicely, and so does the lewd parts. As the story becomes more complex and involving so does the lewd scenes. No matter for which reason you began, you won't be too disappointed with how it develops.
This Light Novel has 3 story arcs across its 12 volumes. The anime covers the first 2, leaving only the last one behind.
While the first 2 arcs are really good both in the story and ecchi departments, the last part leaves a lot to be desired. Stakes that were present during the majority of the story are suddenly gone because they became inconvenient and the battles become confusing with the sudden addition of new things that weren't present before.
There are also other things that contributed to the last part not being all that great, but I won't dive into them since they would be spoilers. Just know that, if you're a bit sensitive on some topics, maybe let this one pass.
If you're willing to see these characters' stories to the end, then give this one a try. But if you're here just for the ecchi, then maybe stick with the anime.
