Just a bit unstable

Haruka is an energetic out-going high school girl. She lives in Tokyo, Japan and she has two best friends that she could always rely on; Kenta and Daisuke. Unknowingly, Haruka has a secret admirer... Well, let's rephrase that. She has a stalker. Haruka starts to feel uneasy like she's being watched which causes her to become a little paranoid so she turns to Daisuke and Kenta for help. One morning the teacher was taking attendance and she calls an unfamiliar name, nobody responds. That piques Haruka's interest. Who could this person be? And why are they absent?