Ruby Hoshino

Ruby Hoshino「星ほし野の瑠る美び衣い, Hoshino Rubii?」, more commonly referred to as just Ruby「ルビー, Rubī?」, is the female protagonist and one of the titular characters of Oshi no Ko. In her previous life, she was known as Sarina Tendouji, a terminally ill patient who was cared for by Gorou Amamiya and, following her death, was reincarnated as the child of her favorite idol, Ai Hoshino.

Neglected by her parents in her previous life and being a fan of Ai, she greatly enjoyed her new life, with her new mother teaching her how to be an idol from an early age. Her mother's life was almost ended when she was attempted to be murdered by a deranged fan but was saved by a mysterious cartoonist. Afterwards Ai decided to retire from the entertainment industry but wanted her children to follow her path, determined to fulfill her mother's dreams, she reformed Ai's idol group with the support of her friends.

Appearance: Ruby is a beautiful young girl of average height with blonde hair that she ties in a side ponytail (much like how her late mother Ai Hoshino does) and possesses pink-ruby colored eyes with a six-star on her left eye like her late mother.

Ruby has been stated to resemble Ai by many people, such as Aqua Hoshino and Kana Arima where Kana herself confirmed that her keen nose in industry "can sense potential in this girl" and it reminds her of Ai. The resemblance grows stronger when she wears a purple wig, to the point that it shocks others especially Akane Kurokawa.

Personality: In her past life, Ruby was a frail girl who died of anaplastic astrocytoma and could barely walk a few steps without stumbling. Now overwhelmed with joy as Ruby Hoshino, the daughter of her favorite idol, Ai Hoshino, takes her life to the fullest, Ruby has given herself the goal of becoming an idol singer, not only to follow in her mother's footsteps, but also to fulfill her promise to Gorou Amamiya. Unbeknownst to her, Gorou had already passed away and been reborn as her older twin brother, Aqua Hoshino.

Unlike Aqua who is calm, calculated and discreet, Ruby is the polar opposite of him as she is extroverted, outgoing, loud, optimistic and communicative compared to her brooding brother. She is most apparent in the connections she makes with others. At the same time, Aqua only does this to further his agenda. She doesn't share her brother's opinion of hunting down the culprit who attempted to kill their mother, instead moving on from that incident and focusing on her dreams. She persists in this notion to the point where she often conflicts with her brother's interests.

Ruby tends to speak her mind without a filter, often referring to Kana Arima as the "gourd girl" and the "girl who will lick a lying snitch," much to Kana's displeasure. Additionally, Ruby has utilized the "airhead sister" persona to her advantage in the media as a character she created to promote herself.

She is the biggest defender of her mother Ai's secrecy and reputation.

Abilties: Ruby's greatest asset has repeatedly been noted to be her natural beauty, which she inherited from her mother Ai Hoshino. Kana Arima also claimed that she has a charisma about her that draws people in. In addition, her mother taught her how to dance from an early age and even Aqua Hoshino noted that she indeed possessed a natural talent. However, Ruby lacked in arguably the most vital area for being an idol: singing; only scoring a mediocre 38 at karaoke. She also held herself back by refusing to resort to any underhanded tactics, causing Minami Kotobuki to believe that Ruby was too "pure" for the cutthroat entertainment industry.