Kouko Kaga’s personality changes depending on the people around her. Having been raised in a wealthy household, she speaks in a formal and refined manner, often appearing strict and elegant. When interacting with strangers, she is polite and composed, but her true personality comes out more around those she cares about, particularly her love interests. She is deeply devoted to the person she admires, pursuing them with unwavering determination and often becoming overly attached. This strong focus sometimes leads to possessiveness, as she can be clingy to the point of stalking. Although she realizes that her actions may be overwhelming even for the people she likes she struggles to change. She also has difficulty controlling her emotions in romantic situations. For example, when she finds out that Mitsuo Yanagisawa has transferred to a new college, she initially intends to congratulate him with a bouquet of red roses but ends up hitting him with it in frustration. Similarly, she reacts with jealousy and hostility toward other women who show interest in the person she loves.

Despite appearing cheerful and confident, Kouko often feels lonely. Many students at her college are intimidated by her wealth and appearance, making it difficult for her to form friendships. Additionally, her strong focus on love has prevented her from reaching out to others, leaving her socially isolated. Even when she does form friendships, she takes time to fully trust and accept them. She also struggles with low self-esteem, seeing herself as awkward and burdensome to those close to her. Beneath her composed and mature exterior, she has an immature and emotionally vulnerable side that she rarely shows.

Kouko’s relationship with Banri Tada reveals more about her personality. Unlike with Mitsuo, she quickly becomes comfortable around Banri because he is open and friendly toward her from the start. She begins to rely on him more and gradually shows him sides of herself that she had kept hidden from others. Her devotion to him is clear through her constant efforts to impress him and become a better girlfriend. However, she avoids direct confrontation in their relationship when Banri worries about her or upsets her, she either blames herself or chooses not to discuss it. These behaviors stem from her insecurities and fear of abandonment. Although others reassure her, she continues to doubt her worth as a romantic partner and worries that Banri will eventually leave her. Her anxieties grow stronger when she learns about Banri’s retrograde amnesia and his past with Linda, leading her to frequently seek reassurance about his feelings.

As their relationship progresses, Kouko becomes more involved in helping Banri deal with his past and emotions. While she remains emotionally sensitive and prone to self-doubt, she genuinely wants to support the people she loves. At her core, she is a kind and caring person who, despite her insecurities, always tries to improve herself for the sake of those around her.

Kouko Kaga has long, wavy, light caramel-brown hair that reaches her waist, with slight curls at the ends. She typically wears her hair down and rarely ties it up, except for occasions that require a ponytail or bun. She has dark hazel eyes and a well-proportioned figure.

Known for her fashionable style, Kouko frequently wears stylish outfits and is almost always seen in high heels. She also favors pink lip gloss or lipstick as part of her daily look. Due to her wealthy background, she can afford to keep up with the latest fashion trends, which often makes her stand out among her university peers. Her sophisticated appearance and confident sense of style intimidate many of the female students at her college.

Kouko Kaga has been childhood friends with Mitsuo Yanagisawa for as long as she can remember. The two attended the same elementary school and high school, and even took a calligraphy class together. However, despite their long history, Kouko’s romantic feelings for Mitsuo were largely one-sided.

Determined to stay by his side, Kouko secretly followed Mitsuo to Tokyo University of Law, having discovered that he had misled her about enrolling in their affiliated college after high school. She suppressed her frustration for four months but finally confronted him during the university entrance ceremony, dramatically slapping him with a bouquet of roses upon seeing him happily walking with Banri Tada.

Due to her persistent pursuit of Mitsuo, including stalking habits and an intense, almost obsessive affection, Mitsuo continuously tries to avoid her. His repeated attempts to distance himself, however, do little to deter Kouko’s devotion at the start of the series.

Banri Tada
Kouko first meets Banri Tada outside the university entrance, moments before she slaps Mitsuo Yanagisawa with a bouquet of roses following the college entrance ceremony. While Banri finds her attractive at first sight, she does not initially hold any feelings for him. Kouko begins spending time with Banri primarily as a way to remain close to Mitsuo, but she quickly grows comfortable around him, becoming more relaxed, kind, and open about her emotions.

In episode seven of Golden Time, Kouko and Banri officially become a couple. However, as Banri’s retrograde amnesia causes his original memories to resurface, he gradually begins to forget their relationship. Unable to cope with the pain of watching him lose his memories of her, Kouko ultimately breaks up with him. Despite this, she does not hesitate to take him back when he regains his memories and reaffirms his love for her.

Mitsuo Yanagisawa
Mitsuo is Kouko’s childhood friend, whom she obsessively loves at the start of the series. However, Mitsuo continuously rejects and avoids her due to her possessive tendencies. When Mitsuo confesses his attraction to another girl, Kouko finally lets go of her pursuit and shifts her feelings toward Banri Tada.

Following this change, Kouko and Mitsuo maintain a friendship, though their interactions are often filled with playful insults and frequent arguments. Despite their past, they develop a more balanced relationship as the story progresses.

Chinami Oka
Kouko initially dislikes Chinami Oka, largely out of jealousy due to her close friendship with Mitsuo. She frequently mocks and insults Chinami, but her resentment is not entirely about Mitsuo—rather, she envies Chinami’s natural ability to make friends, something Kouko has struggled with for most of her life.

Despite her initial hostility, Kouko gradually warms up to Chinami, although she stubbornly refuses to openly acknowledge their friendship. Over time, she enjoys spending time with her, often helping her and even confiding in her about personal matters. While their dynamic remains full of teasing, Kouko ultimately values Chinami as a friend.

Kouko Kaga’s growth from an obsessive and insecure girl to a self-assured and loving partner makes her one of the most dynamic characters in Golden Time. Her journey highlights themes of self-worth, trust, and emotional healing, making her a compelling and realistic portrayal of personal growth in romance.

Her stylish appearance, dramatic personality, and emotional depth ensure that she remains a memorable heroine, loved by fans for her passion, vulnerability, and eventual transformation into a stronger person.