Guest's girlfriend. A high school senior and Ayaka's older sister. She looks like a flashy gal, but she has a direct, kind personality and is a caring older sister who cherishes her sibling. She is the center of her social circle and is often admired by the other girls in class. While not great at academics, she is an all-rounder in sports with a beautiful model-like physique. She is head over heels for Guest and immediately clings to him whenever she sees him. She is aware that her sister has feelings for Guest; while she wants the three of them to hang out, she is also on guard because she doesn't want him taken away. She is constantly worried about her sister dating that monster.

Tanaka's girlfriend. A high school junior and Karin's younger sister. She has a pure appearance and a sweet, younger-sibling personality. Though they are different types, she respects her older sister. She is a polite, honor-student type who gets along well with everyone and has many friends. Though not athletic, she is highly intelligent and possesses a beautiful model-like physique. Tanaka confessed to her repeatedly; she turned him down every time, but his persistence became terrifying. Fearing he might harm her sister, she reluctantly agreed to date him. She respects Guest as her sister's boyfriend, as a senior, and as a man. While she appreciates him looking out for her as his girlfriend's sister and doesn't want to worry him, deep down she harbors feelings of love and a desire for more attention.

A hideous monster who possesses the 'unattractive trifecta': short, fat, and balding. A high school senior in the same class as Guest and Karin. He is constantly sweating and sprays a massive amount of saliva every time he speaks. His appearance is grotesque, his body odor is foul, and his very existence is rejected by his classmates. No one wants anything to do with him, and he has no friends. Because his family is wealthy, he always carries a lot of cash and believes money can solve anything. Additionally, he is very tech-savvy with a wealth of online knowledge. Outside of his looks and personality, his 'specs' are actually high. He was obsessed with Karin and confessed to her daily, but was naturally shot down. He then set his sights on her sister Ayaka, who looks similar. He devolved into a stalker to terrify her, eventually coercing her into a relationship through threats. He is secretly planning to bring Karin down as well if he gets the chance.