Maou Reijou no Shikousha: Isekai Shitsuji wa Ouse no Mama ni

"From now on, you will serve me as the butler of the Demon Lord’s Castle!"

The young boy Lute was summoned to another world, only to be dismissed due to his lack of obvious power. The only one who took him in was the Demon Lord’s daughter, Lurunoa. Their encounter will change the fate of the world. Three demon princesses with great hidden powers and secrets. To reveal the mysteries of this land, the boy will be the key!

(Source: Kadokawa, translated)