A fact-bombing survival strategist who calculates reality and sets standards for action rather than being swayed by emotions. Throughout the seasons, he keeps Emotion Cell in check and is the busiest cell, analyzing Yumi's work, deadlines, income, and relationship conditions alongside Writer Cell. He often moves in the opposite direction of Emotion Cell. While Emotion Cell gets soaked in sentimentality and expresses emotions grandly at night, Reason Cell suppresses that flow and demands realistic judgment. They have a polar-opposite relationship where Reason Cell disciplines Emotion Cell with a rod whenever she runs wild at night. He is called 'Reason'.

An INFP-type cell who leads Yumi's internal narrative, feeling emotions deeply and imbuing even ordinary moments with meaning. She is in an alliance with Love Cell and a relationship of mutual restraint with Reason Cell; she can be seen as the core cell that shapes the direction of emotions during Yumi's growth through romance and self-discovery. She is the first to notice what Yumi is feeling right now. Since Reason Cell values rules, stability, and logic, he frequently clashes with Emotion Cell as her emotional waves grow larger. She is called 'Emotion'.

The Prime Cell in charge of Yumi's romantic feelings and the core of the excitement that greatly influences Yumi's actions. Her personality is straightforward and emotion-centered, and she becomes the most active when a romance begins, leading Yumi's heart. This seems to be because Love Cell is a consistently strong cell. She is called 'Love'.

The cell in charge of Yumi's dreams and creative desires, serving as the core axis of the growth narrative that increases in importance as the seasons progress. He is the inner voice that leads Yumi toward the kind of life she wants to create, rather than just romantic feelings. He has now become a Prime Cell. He is mostly called 'Writer Cell' and occasionally just 'Writer'.

In charge of Yumi's style and appearance, she is the cell that boosts Yumi's fashion sense for dates or outings. Connected to the desire to groom one's appearance, she is a supportive and sensory cell that also affects Yumi's confidence. She is called 'Fashion'.

A cell that predicts situations by deducing surrounding circumstances and conflict factors, helping Yumi find new paths. However, due to his deductive nature, his judgments are not always correct, though he helps Yumi by sensing anxiety. He is called 'Detective'.

The cell in charge of Yumi's savings and realistic management, possessing a supportive and practical personality that assists with work. He frequently bickers with Fashion Cell. He is called 'Frugal'.

A star romance novelist. On the outside, she appears to be a neat and indifferent person who doesn't show much emotion, but inside, she has a rich sensibility and a thoughtful personality. Yumi's personality isn't simply that of a "cold person," but rather closer to someone who tries hard to protect her emotions safely. Thus, she may seem cool or nonchalant to others, but within her works, she expresses how she agonizes over even small feelings of attraction or anxiety for a long time.

She weighs situations and makes logical judgments on Yumi's side. In arguments between cells, she determines right from wrong and delivers biased rulings in Yumi's favor. She values realistic judgment over warm comfort, and her MBTI is introduced as INTJ. Logical Judgment and Biased Protection Rather than playing the role of an objective, neutral judge of events, Judge Cell is closer to a guardian who organizes right and wrong from Yumi's perspective. When opinions clash between cells, she steps in to argue, and she acts based on her own judgments rather than worrying about what other cells think. She is mostly called 'Judge Cell,' but very rarely just 'Judge'.

A giant cell representing Yumi's appetite in Yumi's Cells, characterized by the rice cake skewer on his head. His personality is simple and intuitive; even in urgent situations, he leads the atmosphere with an "eat first" attitude, serving as a stress reliever and energy source. He is called 'Hungry'.