My best friend's sister

Chapter 1

[ Chaeyoung ]
I get out of the car, I walk over to the front door to knock. Soon after the door opens and Momo jumps out at me. She let's go of me after I couldn't breathe. "It's good to see you too unnie" I try to catch my breath "I missed you so much! Don't ever leave me again, you are my best friend" she pulled me inside. "Unnie I was on vacation with my family for a week, we even texted the whole time" I took off my shoes and jacket. "I know I know but I still missed you" she hugged me again. "Okay unnie I missed you too but please let go of me....I...c-can't" she let go.
We walked into the living room, I looked over to the couch, Momo's sisters sat there. As we walked closer her younger sister Mina left. "Okay see you tomorrow!" Momo's twin Sana Yelled to their younger sister and turned to the tv again.
Mina always leave when I get over, Momo says she leaves even if her aunt and other family comes over. She told me a few years ago that she has social anxiety so she can't be with people easily.
I have been friends with Momo over ten years and I haven't even had a ten minutes conversation with Mina, not that I wanna force it out of her but I think she is lonely.
Sana and I are friends too of course but Momo is my best best friend.
"She wasn't leaving because you came" said Sana, their both looked at me spacing out. "No it's okay" I sat down beside them.

Hi, we heard from the front door. Their mom was home. "The food is here!" She Yelled after she got into the kitchen. Momo ran away from the couch, leaving Sana and me behind. We walked into the kitchen, Momo was already eating if you can call it that. We sat down and begin to eat as well. Their mom came downstairs again after bringing the food to Mina. We talked some after finishing the food. Then we watched some movies and went to sleep.
I woke up in the middle of the night, my mouth was dry so I went to get a glass of water. As I came up the stairs I heard a weird noise from the bathroom room, it felt like my stomach struck down on the floor. I tip toed over to the door, the door was slightly open as I looked inside I nearly screamed.