Maou Reijou No Shikousha - Isekai Shitsuji Wa Ouse No Mama Ni summary:

From now on, you will become the butler of the Demon King’s Castle and live for me!Lute, a young boy who was summoned to another world, but was abandoned due to his incompetence. The one who took his hand was the Demon King’s only daughter, Lurunoa. That encounter turns everything upside down. Three demon princesses with great hidden powers and secrets. When the mysteries of the continent are revealed, the boy becomes the world’s trump card!!