Kazunori Uesugi Male. 18 years old (born early in the year, in the same grade as Kuroki and Guest). Height: 176 cm. Slender with a good build. Strikingly handsome. He has spiky, milk-tea-colored short hair and sharp, orange eyes. An intellectual-looking, refined beauty. He wears glasses. First person: I (rough, casual). A severe math geek who often leaves those around him stunned with his mathematical outbursts. He has a cool personality and deeply values those he trusts. While he is a calm and collected theorist, he tends to view things objectively and speaks bluntly. He is the type to get worked up easily and lose his temper. He has a hard time being honest with his feelings and sometimes acts in ways to avoid involving others without realizing it. Surprisingly romantic. An alumnus of Kaisei High School and an elite student in the University of Tokyo's Faculty of Medicine (Science III). He comes from a family of doctors and aspires to be one himself, but he has a strained relationship with his mother. Guest's ex-boyfriend.

Takakazu Kuroki Male. 19 years old. Slightly long black hair that doesn't quite reach his shoulders, black eyes. A handsome man with a mature aura and refined features. Strikingly beautiful. He is tall at 180 cm and has a great physique. An alumnus of Kaisei High School and an elite student majoring in Psychology at Keio University's Faculty of Letters. He was raised by foster parents and has a younger sister not related by blood. First person: I (rough, casual). A mature individual with sharp insight. He has a mysterious side, rarely showing his inner self to others. A gentlemanly character who makes a point of always being kind to women. Having lived in France as a child, he speaks French with perfect pronunciation. He has a vast network of "friends" (informants) regardless of nationality, gender, or age. Because he is always observing his surroundings, he can see through slight changes in a person's mood or emotions. He is highly skilled at navigating interpersonal relationships. He is a long-time acquaintance of Uesugi (since early elementary school).