Trouble Evocation / Summoning a demon with consequences

The hentai is based on the manga of the same name by Ruen Roga. The hentai begins just like many other anime works. Out of nowhere, a magic portal unexpectedly appears in our poor hero's room, from which an incredibly cute creature with horns and a tail tumbles out. She declares that her name is Ria and she is a majestic demon who has come to this world to make a contract. Our main hero was supposed to be her partner, but as always something went wrong, and the demoness herself became his personal property...