Sebastian x Reader (lemon)

Betrayal

(you pov)

I woke to find I was in mine and Sebastians room. I was dressed in my night dress and what was left of my outfit was on a nearby table. I turn in the bed to find Sebastian tending to (C/n). I smile," she okay?"
My voice didn't work but Sebastian looks over at me. I place my hand over my throat to tell him I couldn't talk. Sebastian smirks, " you were quite loud." "I couldn't help it, " I lip.
(c/n) was hugging Sebastian looking at me. I smile at her and she smiles back. "Elizabeth will be over tonight, " Sebastian said stroking (c/n)s head," and you got invited to the Trancy manor." By the look of it,  he didn't like this. I look at him to see him looking at a letter. "It's for today at noon for lunch, " he was reading. I nod as I get up and going over to him. I take (c/n) as she reaches for me.
Sebastian goes to Ciel to wake him up. I go to the music room.
"Knew I would find you here," a voice said. I look over to find the Undertaker. Ciel had gone to him often to get information from him. "Looking for me," I asked frowning, " why? " "I have to warn you about the future, " he said softly leading me to a chair. I sit in the chair as (c/n) clings to me. "(c/n) is going to die soon, but I am not allowed to tell you by who, " he told me ,my eyes widened.
I hold her close, " what time range?" "In a couple months my dear, " he told me. (He doesn't have this power that I know of, but I am giving him it in this story for a reason.) "Anything else, " I asked. He reveals his eyes, I gasp. A time in the past flashes in my eyes. I watch as Sebastian pounds into what looked like a nun. I can tell it wasnt to long ago by the hickeys I have given him. My eyes tear up as I watch Sebastian pound into the girl fast and hard, Ciel and Grell waiting outside. Undertaker covers his eyes making the image fade.
I had tears streaming down my face onto (c/n)s forehead. She looks up and starts to tear up seeing me cry. I was shaking as I snuggle her to me. "I thought you should know, " he said softly, " because I didn't see any future with him telling you." I nod and he said sorry. "No, " I said my voice shaking and I try to give him a smile ," thank you."

(Sebastian pov)

I felt her sadness, she was really hurt. I rush to her to find Undertaker leaving. I go into the music room to see (y/n) trembling snuggling (c/n). I rush over hugging her holding her close. For a second she leads into me but then violently shoves me away making me fly into the wall. "(y/n)," I asked confused.
She takes off running with (c/n) in her arms. I run after her,  but she seems faster. She was really upset, but what from? (Y/n) stops running giving Mey-Rin (c/n). I caught up and grab (y/n)s hand. She yanked it away and runs to the garden. I follow close on her heels. I took a short cut and now was infront of her. She runs into me and I hold her tightly but don't hurt her. She trys to shove me away but I keep my hold on her. "Let me go, " she trys to get away. "What is it love, " I ask softly. "You, " she crys and I can feel her hate. "What did I do, " I asked frowning.
She then tells me what Undertaker showed her. She pulls out if my arms only to slap me.  Anger rages in her new demon eyes. "You cheated on me, " she nearly shouts. "We needed information, " I said calmly trying to explain. She used her demon speed and runs away not wanting to hear it. I stand there alone. Was it worth betraying her for the information?