Odd behavior from sis

It's almost a week by now, everything is fine the whole day in the house. Just when the clock hits around 5 pm something odd happen to my sister, it's like a switch is flipped and her personslity is completely changed. The once shy girl gets a daring attitude and she doesn't care about anything else then locking herself on her room to do god knows what.

I got home early today, I really had to figure this out cause something feels off. "Hey bro, got home early today." She says with her soft voice. "Sure sis, I finished work early so I could help you out with the house." I said looking at the clock and seeing there was a hour left until it hits 5 pm. I made some chores with her like washing the dishes and getting the dinner ready, everything seemed normal so I asked her about how she was feeling lately.

"Being honest, I'm having a hard time studying lately, no matter how much I tried the subjects don't seem clear as before, maybe I should rest more." I knew something was not right, she was not even studying in that time gap cause every time I asked she would say she was doing something else. When I asked her about it she was sure she was doing chores or studying in that time.

I check my watch and there's just less than a minute to the usual time. "Sis, can you see if there's something on my face, it seems itchy near my nose." She nods with a smile and get close to me, her eyes checking me out with care as they suddenly open wide. "So, you want a kiss or what?" She laughs at me and go to the kitchen, grabbing an apple to eat.

"Don't you remember? You were fixing my hair." I said while focused on her reaction. "Oh sure, nevermind. Is there some pizza left from yesterday?" She asks bending over to watch carefuly on the fridge, but she gave up on looking and took some other snacks. "I am going to my room, I need to study a bit more so you can finish everything here and call me in the dinner time."

I didn't had any reaction, just watched as she went upstairs with her snacks. "That's not my sister." I said to myself. I went upstairs as well and knocked in the door but she only told me to chill out. I couldn't do anything before wait, so after some time I finally got her wenting to my parents room. "Hey, I think you know something pal, but you will never guess the truth." She laughs with a toy in her hands.

"Cut the crap, I want you to tell me everything."!" I said angry, but she just put the toy in her room before coming back to the door. "Don't be like that, you will make her suffer even more." What? She's really talking like someone else. "I'll have my fun as aways and leave her alone, you should thank god I am a nice person, any other one would do unthinkable acts to her." She closes the door with a naughty smile leaving me dumbfolded, with way more questions from now on.