Kaguya Shinomiya grew up in a strict, neglectful household where her brothers are amoral bastards, her father doesn't care about her at all, and her mother died when she was very young. Her only true friend growing up was her personal valet, Hayasaka, and they were forced to act like they didn't know each other outside of the household. She has severe trust issues, often subjecting her potential friends to tests to see if they are trustworthy, which most of them fail. One friend admitted she only got close to her because her mother told her to. When she fell in love with Shirogane, she tried to bury her feelings out of the belief that someone as cold-hearted as herself was unworthy of his love. Later on, she learns her best friend Hayasaka has been reporting her every activity to the Shinomiya family's main household for years, severely betraying her trust.
Miyuki Shirogane's mother abandoned him after deciding he wasn't smart enough to meet her standards, and his father is seriously in debt and living in Perpetual Poverty, giving him abandonment issues and a complex about pleasing others. He falls in love with Kaguya, and becomes convinced that she'll only love him if he became perfect. So, he spent week after week for over a year working himself to exhaustion to become as close to perfect academically as he can despite his fundamental lack of talent at most things. He hangs up all kinds of "motivational posters" in his room to push him to keep working, even when he can barely stay awake. And he does all of this because he's convinced that, if people discovered how flawed he truly was, nobody would love or respect him.
Miko Iino has been ostracized by her peers since she was in grade school for her straight-laced enforcement of the rules, often times getting so bad that she had to run where nobody could see her and cry. Her parents are rarely around, and she had no friends but Osaragi when she first started out in high school. Then she fell in love with Ishigami, only to have to watch him pine for another girl. She copes with this through various unusual methods such as writing dark sutras or listening to CDs of boys complimenting her. Her friends are worried that she'll get trapped in abusive relationship somewhere down the road, since she's so completely starved of affection that she'll let people walk all over her as long as they feed her a compliment every now and then.
Yu Ishigami discovered that an acquaintance's boyfriend was cheating on her, and when he punched him out for it, he made Ishigami out to be a violent stalker, turning him into a social pariah for almost two years. He has to contend with distrust and backtalk on a regular basis, and his female friends are often pressured by other girls to not hang out with him. Hardly anybody cheered for him whenever he won during the Sports Festival, culminating in his acquaintance from the past, Otomo, coming back to belittle him as well. He bottles it all up since if anyone ever learned the truth behind the incident, Otomo's optimism would be shattered, and he wishes to protect her smile over his own reputation.
Kobachi Osaragi alienated her jealous peers with her fame and youthful looks as a child idol. When her mother was caught having an affair that was then made public, her classmates offered false compassion, when they really felt she deserved it out of jealousy over her good looks. It's implied she dresses so plainly nowadays so as to avoid attracting any more jealousy.
Papa Shirogane was once a highly successful businessman, until he lost his company and fell into an over 500 million yen debt, condemning himself and his family to a life of poverty. His wife left him and took their daughter with him, and he has to contend with the fact that despite his best intentions, he ultimately failed to provide adequate emotional support for his son as he fell into a borderline self-destructive crusade against his own flaws. He hides his pain with wacky antics, but it's clear that deep down he's a broken man.
Ai Hayasaka grew up as a servant to the Shinomiya household and has served as an aide to Kaguya for 10 years ever since she was 7. Since Kaguya's household lack a head butler/maid, it falls on Ai's shoulders to manage the other servants and ensuring that their work meet the insanely high standards imposed by the family. Her schedule is packed from 5 AM until past midnight, and it is implicitly stated that the sheer amount of responsibilities placed on her shoulders violates several labour laws. She's also wracked with guilt over having to leak every detail of Kaguya's personal life to her eldest brother, knowing that she's betraying Kaguya's trust as her confidant. Even at school, she is unable to enjoy a normal life, since she is forced to act in a completely different manner than her usual demeanour in order to maintain a distance from her true role/identity, and this results in her inability to form genuine friendships with her school companions. However, aside from occasionally snarking at her master's antics, Ai rarely gets to express her discontent about her job and her life in general.
