2girls, ahoge, arm behind head, arm up, arms behind back, bow, bowtie, choker, closed mouth, empty eyes, expressionless, feet out of frame, greyscale, long hair, long skirt, long sleeves, looking at viewer, looking down, midriff peek, monochrome, multiple girls, neckerchief, no pupils, parted bangs, pleated skirt, sailor collar, school uniform, serafuku, siblings, side ponytail, sidelocks, simple background, sisters, skirt