When he wakes up one morning, the protagonist who is an only child, finds himself having an older sister―― She has tanned skin and a voluptuous body. While being confused, she takes his underwear off as a matter of course, and gives him a blowjob.
My brother's sperms belong to his sister...... Having said that, she starts sucking his cock.
Is this a dream, or is this some kind of delusion――
But in reality, his self-proclaimed sister―― Is a demon who has been summoned to this world accidentally～a succubus.
The demon calls herself Leviola, because she needs human life force in order to return to her world, she puts his cock into her mouth and sucks him harder.
Let me have plenty of your sperms♪ Having said that, Leviola smiles.