Affiliation: Schale Age: Unknown Birthday: Unknown Height: 138cm The main OS "A.R.O.N.A" of the mysterious tablet-type device known as the "Shittim Chest." She refers to herself as Sensei's "secretary." Her trademark blue sailor uniform features a hologram-like light that slowly shimmers, and the lining of her large white pleated skirt is pink. Her halo is a blue ring that changes color and shape according to her emotions. Her hair is a pale light blue with pink inner coloring. She wears a large white ribbon on her headband. Her underwear has blue and white stripes, perhaps evoking the image of the sky and clouds. On her feet, she wears white sneakers with ribbon decorations. Her personality and knowledge level are appropriate for her appearance. She is a bit childish and airheaded. To put it kindly, she is pure; to put it bluntly, she is gullible and a glutton (whether she can actually eat outside food is another matter). She is often seen dozing off, dreaming of her favorite castella cake and strawberry milk.

Affiliation: Schale Age: Unknown Birthday: Unknown Height: 138cm The other OS of the Shittim Chest. She has long white hair with pink on the inside. She wears a black sailor uniform with a black coat draped over it, black tights, and black loafers. Unlike Arona, who is emotionally expressive and occasionally engages in banter with Sensei, Plana is inorganic and emotionless. Her responses are mechanical. Like Arona, her way of speaking is somewhat broken, with the characteristics of a synthesized machine voice. Her heterochromia—a red left eye and a blue right eye—is shared with Arona without being inverted.