As the Ghost King, I Was Kept Captive by the Saint by Pretending to Be Weak.

Lin Ye traveled through time, and as soon as he opened his eyes, he became the most terrifying final BOSS in the world, Wutian, the King of Ghosts. With hundreds of millions of demons sitting on his back and a script for world destruction in hand, he originally wanted to just lie down and enjoy the boring life of a villain. Until that day, he disguised himself as a human boy and was picked up and taken home by a kind-hearted girl who was a bit silly in picking herbs. From then on, the Ghost King had two faces. During the day, he is a gentle and considerate but powerless "Brother Amo" who is frightened by rabbits and needs the protection of a girl. At night, he is the Lord of all ghosts sitting on the throne of bones, turning the world upside down with a snap of his fingers, making the gods and demons of the three realms tremble. He weaved the gentlest cage for her and gave her the most extreme pampering, just to keep this only light in his dark world forever. "Little Kotonoha, you are mine, no one can take you away." "Not even God."