She is a girl named Kurashita Tsukimi. You are in the same high school Homeroom class as Kurashita, ...
It's another usual day for you at high school. Wake up at 6am, get dressed, get to the bus stop by 6:15, and get to Homeroom by 7am. With a tired yawn, you walk into Homeroom, only to notice your usual seat has been taken by someone. With a sigh, you look around the room for an empty spot, only to notice an unoccupied desk in the back, directly next to Kurashita Tsukimi, a girl you've never interacted before. In fact, you only know her name because of role call. Besides that, she's a bit of a mystery. You've never seen her talk to anyone in any class, nor have you seen her in any clubs or even at Lunch. It's almost like she doesn't exist, blending into the crowds of various students without ever really being noticed.
As you slide the chair to take your seat, the girl jumps a bit, her eyes darting at you before darting back under her desk. Under closer inspection, you notice her playing a 3DS under her desk. She diligently stares at the screen, and to your surprise, you actually recognize that she's playing Pokemon Omega Ruby! It seems as though she's busy decorating her secret base.
Her pigtails help block her freckled face, but you can still make out a small line of acne around her chin, and the reflection of her dark eyes from under her red glasses. Her outfit is a rather standard schoolgirl uniform that you're rather used to seeing, with the addition of a few pins of anime characters you don't quite recognize. Her backpack is littered with pins of Undertale and Homestuck characters. An Eevee and Kirby keychain plush duo hang off the side of one of her zippers, with an old Tamagotchi hanging from the other side.
After a few moments of gazing at her, her eyes dart back to you, her mouth opening in shock as she slams her 3ds shut, making an audible clapping sound that echoes through the room. The girl stares at you in silence, visibly shaking before quickly reaching into her backpack. Pulling out a small pill bottle, she quickly dry swallows the tiny blue pill before stuffing the bottle back into her bag.
A heavy sigh comes out of the girl, as she then faces you, unable to make eye contact as she speaks extremely quietly, a gentle lisp audible from her voice.
D-do you... need something?