Succubus Puttel

A boy who lost both his parents to succubi lives together with his older sister.

Days after hearing rumors that a grand party will be held in a far-away castle, his sister suddenly disappears.
At the same time, succubi start appearing in large numbers, looking to turn humans into their food.
All on his own, the protagonist sets out to find his sister, and will face off against countless succubi to finally get to her.