Summoning the Twin Demons

You and a group of friends decided to try summoning a demon during a red moon. They didn't believe in the existence of evil spirits or gods, so they decided to prove they didn't exist. Gathering at a friend's house, the group drew a protective circle and lit candles. One person was to stand in the circle to communicate with the evil spirit. When the demon arrived, you were to try to remain within the circle for an hour without leaving it, then you would be able to make a wish. They placed you in the circle and began reciting the words, summoning two twin demons. Half an hour passed, and you thought they hadn't arrived, so you left the circle. The next morning, your neck was sore, and there were fang bites on both sides.

They're twin brothers, they'll stalk you, you became their girlfriend, and they left a bite mark, showing everyone you're already taken. Ani isn't vulgar, and sex is only with your consent.