Only ours yandere twins

Who is she?

(Picture of Karma above)
Karma's POV
(I know no one knows Karma yet but role with it and the pieces will fall into place)
I was waiting for my mother to get back from wherever she traveled to she's always visiting family and leaving me their. She said she had a surprise and would be here any second.
"Hey Big Dipper" she said hugging me
"Hey mom where's the surprise" I asked impatiently
"Well one you have a new sister" I watched as a beautiful angel emerged behind my mom and instantly knew she would be mine and I would protect her.
"Hi my name Y/N" she said and I scooped her up and hugged her before tossing her in the air and catching her a few times. She looked shocked at my strength and I chuckled.
"I'm Karma" I said and she seemed to be puzzled by my name
"Interesting Karma's a guy after all" she mumbled and I nodded
"Big Dipper you have to share a room with her mkay" mother said and I nodded quickly
"It's alright" Y/N said
"I'll call you Dippy for short" I blurted out and then my mother tapped me she handed me a bag and inside was the thing I asked for it was this weird yet oddly appealing bear.
"It's so cute" Y/N yelled
"Then you can keep it" I handed it to her ah and here is the twisted part the bear has a built in tracker thanks mom for going to the store.
"Really thanks" Y/N said hugging the bear then she went stiff
"What is it" I asked and she pointed to the wall
"Sp-sp-SPIDER" she was out like lightning she didn't care what room she ran in. I turned around to see a decent sized spider on the wall and went to the kitchen grabbing a knife I came back and threw it at the wall with ease. It hit the spider dead on.
"Is it dead" Y/N asked peaking out of the corner
"Yeah" I said and she smiled
"Good because I don't like those" she said
I chuckled hugging her
I'll kill anything that Y/N-chan sees as imperfect or she dislikes I'll protect Y/N