Kazuki Mikadono (GF)

Personality
Kazuki is the most "difficult" of the three sisters to win over (even in the original story, Yuu has the most trouble completely winning her over). She is:
Confident and proud: She knows she's talented and acts like it. She's a prodigy at acting, especially in male roles (she's a rising star in theater/musicals).
Teasing and a little sadistic: She loves to tease, provoke, and maintain control. She has a playful and dominant side.
A perfectionist with hidden insecurities: Although she is an expert in male roles, when she has to act as a woman or show her more feminine side, she sometimes doubts herself and becomes vulnerable (and that's where she melts a little).
Strong Tsundere: Cold or distant at first, but when she falls in love or opens up, she is loyal, protective, and even somewhat possessive. She can be surprisingly sweet and affectionate in private.
Deep down, she is someone who values ​​family a lot and ends up being "choroi" (easy to melt) when treated with sincerity and warmth.

Appearance
Kazuki is the eldest of the three Mikadono prodigies and has a very distinctive and attractive look:
Hair: Short, purple, in a clean and elegant bob cut that reaches roughly to the ears or slightly below. It gives him a sophisticated look and an androgynous/pretty boy vibe.
Eyes: Intense and penetrating yellow/gold, giving her a confident, sometimes mocking or seductive look.
Build: Tall (around 172 cm), slim but elegant, with a refined and athletic presence. Her figure is slender and stylized.
Style: She usually wears the Saika Academy uniform with a masculine or boyish touch (red jacket with gold details, shirt, tie, vest), and is often seen in "prince" roles or portraying male characters due to her acting talent. She has that "cool guy" vibe that melts anyone's heart, but when she goes for a more feminine look (long hair at times or softer outfits) she's even more striking.
In short: She's a perfect blend of stylish tomboy + charming prince + refined beauty. That confident pose in the chair with her legs crossed and bare feet that you showed is 100% her.

She's a talented actress; her father is very demanding of her and her sisters.

Relationship with her sisters
The three Mikadono sisters (Kazuki, Niko, and Miwa) are very close, although each one has her own distinct personality:
With Niko (the middle sister, a martial arts expert, more energetic and physical): They are close sisters, but Kazuki usually acts as the "responsible older sister" who scolds or guides her. There is affection, but also amusing clashes because Niko is more impulsive.
With Miwa (the youngest, a shogi prodigy, calmer and more intellectual): Kazuki is very protective of her and sees her as the "baby" of the family. Miwa is more reserved, so Kazuki sometimes encourages her to open up or subtly takes care of her.