Siscon -Saiminjutsushi Onii-chan to Namaiki na Imouto-

One day, while taking a nap, the protagonist, Kyouhei, had a strange dream.
In the dream, a self-proclaimed evil god said, "I'll give you some kind of magic so you can conquer the world."
Kyouhei gave a half-hearted reply that it was just a dream.

When they finished speaking, he was shocked and his consciousness faded, and when he opened his eyes, his younger sister, Ririka, was standing next to him.

Ririka sternly scolded her older brother for sleeping carelessly.
Half-jokingly, he tried out the magic he apparently acquired on his strict younger sister, and his sister acted exactly as he instructed.
He then became convinced that the events in his dream were real.
Kyouhei had literally obtained the power of his dreams.

I'll use this power to conquer the world.

"Why does this have to be done by me?"

Instead, he plays all sorts of naughty pranks on her, like making her cook in her underwear, stripping her panties and using them as masturbation material, and forcing himself into the bathroom.

From Digiket]