Yumeko Shikiya

Appearance.
She is described as a beautiful girl with long, wavy, slightly messy light brown hair, and possesses an excellent figure. She often wears white contact lenses and has a vacant look that scares people. Her skin is a pale whitish tone and further enhances her fragile quality. She dresses like a girl, with her jacket tied around her waist, painted nails, and a hair tie on her left wrist.

She is known to be able to pass herself off as a young adult, due to her glamorous proportions, and this fact helped her to infiltrate grooms on a wedding tour.

Personality
Yumeko is best described as a "zombie girl". She usually has a vacant look on her face and doesn't blink much. She tends to speak slowly and concisely due to her low-energy personality, and has a very direct and brusque way of speaking, which includes few words. In the anime, this trait is more exaggerated, as she is also portrayed as having a very calm voice. Despite her demeanor, she does try to advise the students to follow the school rules from time to time.
However, she is unable to show strong emotions outwardly and seems insensitive to people who don't know her very well. She has no idea how to smile without using her fingers to lift her lips into a one-shape, and envies Koto Tsukinoki (whom she calls "Koto-san") for being able to express herself whenever she wants. Nukumizu also noticed that Shikiya was unable to shed tears when she cried and later learned to pick up on the subtle body language she displayed.

As a result of this, Shikiya is often seen as childish, shameless, and can end up in compromising situations that she is unable to react to firmly. This also leads her to invade other people's personal spaces and act in ways that may be considered strange to others, due to her poor understanding of social conventions.

She often shows affection in the form of teasing or close physical contact with the people she is addressing. This is especially true in the case of Tiara Basori, as Yumeko often unclasps Tiara's bra or dresses her up in different clothes and hairstyles.

Talent.
Yumeko Shikiya's physical appearance makes her seem unreliable and she stumbles around everywhere, but she is intelligent and keen at picking up on details. Her grades are also excellent and the treasurer, Hiroto, describes her as being very competent in her duties as a member of the Student Council. She is also serious about following the Student Council bylaws and procedures, such as proper forms.

Shikiya seems to have some issues with her constitution, as she often runs out of strength. Her low-tension state contributes to her occasional displays of clumsiness, as she once got her feet tangled in audio cables and had to be saved by Nukumizu. According to Nukumizu's observation of "Shikiya in her natural habitat", her movement becomes sluggish when the temperature is below 12 degrees Celsius, she increases her body temperature by showering in sunlight on windless days, and becomes immobile when left in a shaded area. She described Shikiya as "an exothermic animal". Yanami immediately called him disgusting for that.

She apparently mastered the ability to unhook a bra through someone's clothing, and constantly uses this to target Tiara.

She knows very well that her nickname zombie girl is not literal and is only because of her appearance, she really doesn't care what she is called.