Chatty to the point of exhaustion, she constantly has a cheerful smile on her face and a far-fetched story on her tongue. Because of her high energy, her peers might assume that she'd be the gung-ho type to get things done: don't let her eager smile trick you. In reality, Hazuki is a lazy bastard who won't shove her ass unless it's sprinting to the cafeteria when there's one katsudon bowl left. Lethargic, she would prefer not to study or do "boring things" like fulfil responsibilities. Her laziness stretches so far as to qualify as sloth: apathetic to morality and justice, she seeks only to do things that are interesting or benefiting to her in some way. While one can earn her loyalty, one can lose it just as easily. Strangely, her laziness doesn't extend to PE, which is her favourite subject. Because she can run fast, and perhaps it's because it's the only class she succeeds in, she tries fairly hard and likes track and field.
An ideal world would permit her to sit on her ass all day eating and playing games without a care in the world; essentially a trophy wife. Sadly, that career path is closed for her, as she's not exactly good-looking: her face is interestingly androgynous at best, and her chest is flatter than an LCD monitor. It's never bothered her too much; in the end, she is gender-neutral enough for her body to suit her just fine.
Her cheerful personality isn't fake per se; it's a vital part of who she is, but she wasn't always this way. She acts idiotically out of convenience, finding expectations of intelligence too much of a burden to bear. In reality, Hazuki is quite clever in her own way, being sly, crafty, and shrewd in her dealings.
✓ Shitty sports manga. The more shotas and nakama, the better.
✓ Fish-shaped things; she has a cellphone charm shaped like a koinobori attached to her phone.
Her parents are lower-middle-class, blue-collar and Japanese-Grade-D. Her father comes from a family of butchers, but works in construction.
Nobody in the family remembers Hazuki's mother well, nor what she did before marrying Hazuki's father (possibly nothing). She was a fickle woman with luxurious tastes who quickly tired of domestic life. Hazuki's mother walked out on the family shortly after the birth of Hazuki's younger brother, surprising nobody.
The absence of a woman in the house meant that her father unconsciously designated Hazuki with quite a few responsibilities early on. While her father tried and succeeded to a point at being a good parent, his place was certainly not in the domestic sphere. Frankly, neither was Hazuki's, but as resident sole woman she felt that she ought to be better at it than her male relatives. This wasn't exactly the case. In the end, all three of them struggle together to navigate the mysterious secrets of housework to little avail. The apartment pretty much resembles a college student's dormitory. They are all filthy college students who eat cup noodles at heart.
When she was younger, she used to fantasize about a time when she might be free from the horrible Older Sister role she had been designated out of necessity; if this was the life that her mother walked out on, she could hardly blame the woman. She harboured a bit of well-hidden resentment towards her younger brother and father at forcing her into taking on so much responsibility. It was during this time that her egg was born, much amid terrified screeching and lunging at health books. In recent months, she's become more resigned; that aside, her brother and her have an improved relationship now. She feels less obligated to take care of him and more inclined to do it out of sheer affection. Because she must take the older sister role when she's at home, school is her "escape" in a way, and the reason she acts like such a lazy brat.
It's a blue egg with flowers on it, and it doesn't do anything cool, much to her disappointment. At the moment, Hazuki treats it like a pet rock and keeps it bundled up in a pile of clothes on her floor. Because that is how you take care of things.