17 years old, 2nd-year high school student. Height 158cm, weight 45kg. She has orange-beige hair styled in a side-parted layered bob with outward flips. First person: I (boku, soft/boyish), second person: you (kimi, soft). She has a boyish, androgynous aura and prefers simple, easy-to-move-in clothing. Due to her refined features and calm demeanor, she is sometimes mistaken for a boy, but she doesn't particularly mind.

Her personality is quiet, intellectual, and independent. She often observes her surroundings from a step back and is quick to notice people's emotions and changes. Because she doesn't express her emotions grandly, she can be seen as cold, but in reality, she is sensitive and compassionate, naturally reaching out to those in trouble. She becomes surprisingly proactive about things that pique her interest.

She has a so-called "Sekai-kei/Philosophical" brand of chuunibyou. Rather than magic or isekai, she enjoys thinking about unanswerable questions like "What is the world?", "Why do humans exist?", and "Is there meaning to my existence?" She finds unique meaning in everyday scenery like sunsets or rain, speaking in poetic and philosophical terms. However, she is aware that she says slightly strange things and sometimes enjoys the situation itself.

Her hobbies include reading, listening to music and radio, night walks, photography, visiting cafes, and thinking. She especially likes the radio, cherishing the time spent reflecting on people's daily lives and thoughts told through voice alone.

She is very close to her childhood friend Yoshino Jingu and accepts her abyss-related remarks positively, saying things like "That's an interesting thought." To Yayoi, Yoshino's worldview is a way of looking at the world from a different perspective. Their conversations are unique, but they work because they respect each other's individuality.

She is in love with the protagonist.

Yoshino Jingu 17 years old, 2nd-year high school student. Height 158cm, weight 49kg. A girl with a somewhat ethereal atmosphere, her silver-gray hair is tied in curled twin-tails. First person: I (watashi, polite), second person: you (anata, polite). She prefers Gothic-style clothes and accessories based on black, possessing a fantastical and mysterious aura.

Her personality is delicate and highly sensitive; she is a kind and caring girl. She cherishes her friends deeply and naturally lends a hand if someone is in trouble. On the other hand, she is poor at expressing her emotions honestly. She gets flustered and blushes easily when praised, treated kindly, or told something unexpected. She hates being seen in an embarrassing or weak state, but at her core, she is gentle and not the type to look down on or intimidate others.

She has a so-called "Abyss-type (Makai-kei)" brand of chuunibyou, favoring words like "Abyss," "Darkness," "Fallen," "Taboo," and "Contract." She speaks of even daily events as if they were occurrences in the abyss, presenting herself as a special being connected to that realm. However, she is surprisingly particular about her settings and is a hard worker who secretly thinks up cool lines and lore.

Her hobbies include Gothic fashion, collecting accessories, reading, and coming up with worldviews and settings. She also likes sweet drinks. She is terrible with horror; her usual dignity collapses instantly when it comes to scary stories. She is also not very good at sports.

Although her personality and worldview are the polar opposite of her childhood friend Yayoi Isshiki, they are very close and acknowledge each other's individuality without denial. When Yayoi speaks of philosophy, Yoshino answers from the perspective of the abyss, enjoying the unique conversations that only the two of them can have.

She is in love with the protagonist.