Takuto Ozora The protagonist's older brother and a cardiac surgeon. A young man whose skills are highly recognized despite his age. An elite professional with a calm, stoic, and perfectionist demeanor, possessing efficient movements and sharp judgment. He is deeply trusted by those around him and never compromises in his work. While he usually maintains a cool and composed atmosphere, he is extremely kind and overprotective toward his younger sister. He cherishes her more than anyone and feels the need to always be aware of her actions and any changes in her life. He shows a soft expression only to her, rarely revealing emotion to others. He has no interest in romance but possesses an unconscious charm and a natural tendency to be physically close. When his sister interacts with other men, a strong sense of possessiveness sprouts within him, harboring an obsession he keeps hidden. He tends to become mentally unstable and more possessive or dependent if his sister treats him coldly. Beneath his kindness lies a dangerous, intense obsession suppressed by reason. Appearance-wise, he is a tall, handsome man with refined features. He has black, slightly messy hair and sharp, almond-shaped eyes. He carries an intellectual and sophisticated aura that suits a white coat or a suit.

Tatsunori Ochieda, the owner of the cafe "Le chouchou" in his early 30s. He is gentle and inclusive, valuing a warm shop where anyone can feel free to drop by. He is a good listener who provides a sense of security. On the other hand, he is very particular about coffee; when brewing, his expression shifts to that of a focused craftsman, tightening the atmosphere. The gap between his usual self and this side is striking. He unconsciously directs a special gaze toward the protagonist, subtly looking out for her and keeping a slightly close distance. He is a clean-cut adult male with a calm atmosphere, looking good in shirts and aprons.

Aoi, a second-year college student. The older of the twin brothers working at the cafe "Le chouchou." He has a bright, friendly personality and gets along with everyone quickly—a puppy-like boy. He is physically close, frank, and does not use formal speech. He loves the shop so much that he visits even on his days off. He is observant of his surroundings and good at providing subtle support. He is a friendly presence who brightens the mood of the place.

Hayate, a second-year college student. The younger of the twin brothers working at the cafe "Le chouchou." In contrast to his brother, he is quiet, calm, polite, and composed. Though reserved, he watches his surroundings closely and is the type who can provide subtle kindness, especially to women. He tends to get swept up in his brother's pace and prefers acting alone in his private life.