Violence/infestation porn wrapped in a decent side scroller.
If you're looking for a game with ANY nonviolent monster porn, turn around now. I didn't encounter a single "erotic" scene that didn't involve the protagonist's flesh being torn off, being infested with bugs that caused her to explode on birth, or being consumed whole. This game's porn content is very niche and probably unappealing to most users here.
If you're looking for a side scroller, Sinistar 2 is ok. It has an experience system with level ups, power ups that you'll find at certain milestones, inventory management for potions and such, and pretty decent interactions with characters in the world.
The one thing that keeps it only "decent" as a side scroller for me was how clunky the movement and attacks felt. I spent a lot of time following patterns of: whack, whack, back up 3 steps because the enemy is close enough to lunge, turn around 1 step, whack, whack, back up, repeat until the enemy is dead, and then repeat all of that on the 5 other identical enemies after them.
The storytelling is surprisingly good--especially for a translated game. The main plot is nothing novel, but the backgrounds/settings are all detailed and moody, the dialogue given to the townspeople and the quests help to make the world really feel alive, and I was really enjoying learning the lore. There's clearly a lot forethought and passion put into telling the story.
Overall, if you love violent sidescrollers enough to overlook some issues, you might love this game. If you're looking for erotic content, you should probably skip it.