Aqua Hoshino

Ah-kun (あーくん) (By Arima Kana)
 * caption1=
 * name=Aquamarine Hoshino
 * kanji=
 * romaji=Hoshino Akuamarin
 * nicknames=Aqua (アクア)
 * gender=Male
 * height=172 cm (5'7")
 * age=16
 * birthday=
 * status=Alive
 * relatives=Ai Hoshino (Mother)†

Hikaru Kamiki (Father)

Ichigo Saitou (Adoptive Father)

Miyako Saitou (Adoptive Mother)

Ruby Hoshino (Younger Twin Sister)

Taiki Himekawa (Older Half-Brother) Amemiya Gorou (Previous life) Doctor (Previous life)
 * occupation=Actor
 * manga=Chapter 1
 * anime=Episode 1
 * relationships=Akane Kurokawa (Former Girlfriend)

Kana Arima (Friend, Crush)

Taishi Gotanda (Mentor) Yumi Uchiyama (young) }} "The guy who made Ai go through such a thing is in the entertainment world. Since that guy is related to me by blood, I can track him through genetic testing with a piece of hair. I can't die yet. Not until I find him... and kill him with my very own hands."
 * jpva= Takeo Ootsuka

Aquamarine Hoshino, or more commonly known by his stage name Aqua (アクア), is the titular main protagonist of the Oshi no Ko manga series. Aqua was known as Gorou previously, a medical doctor who treated patients. He developed an obsession with idols (specifically for Ai Hoshino, a member of the defunct idol group, B-Komachi) after encountering Sarina, one of his patients holding the same infatuation. He was reincarnated along with his twin sister Ruby Hoshino, also formerly known as Sarina, and is now the child of Ai Hoshino.

In Aqua's new life, although dumbfounded by the situation, he enjoyed being Ai Hoshino's child. His wit and conversational skills while a child disturbed various people in good ways. Such as an award-winning director, Taishi Gotanda, who swiftly praises him for how much he talked. These skills greatly serve him throughout his childhood, and even to the present. Aqua also enjoyed a privileged life. He lived luxuriously due to being a child of a famous idol, and he enjoyed watching his mother perform. A good life which, unfortunately, ends after a deranged fan of Ai commits a terrible atrocity towards his family.

This event would fundamentally change Aqua. He swore he'd do anything to find whoever was behind the tragedy. Despite numerous years passing, he is unrelenting in his goal, unlike his sister. Many of his actions were driven by this very ambition. He is willing to do anything to get closer to the truth including committing acts that teeter incredibly delicate lines.

Appearance
Aqua has blonde hair and is relatively tall. He has blue Aquamarine eyes, which is what his mother named him after. He often changes his appearance due to his job as an actor. He is described as "handsome" and features a star in his right eye; symbolizing that he and his sister are one halves of their mother. When he was a child, he was often called cute by those around him.

Due to him being Ai Hoshino's son, many people were able to point out their similarities despite being unaware of his pedigree. Much to Aqua's dismay; as, prior to Chapter 105, he wanted to keep the truth of his late mother from being known to the general public.

Personality
Before the tragedy that struck his family, Aqua was considered relatively normal other than his unparalleled prodigious talent in acting even as a child and his quick wit and intelligence. With him retaining his past experiences, he accomplished many things not expected for someone his age. Performing acting jobs was something he was open to and excelled at.

After the tragedy, he transformed. -- becoming cold, calculated, cunning, and discreet; A man willing to do whatever means necessary to see his goals through. The pain he underwent tends to resurface anytime he seems to forget his goals. This is the case when Kana Arima suggested that he'd look back at his happy memories in Chapter 50 to improve his acting on the spot. It is a case of Post-Traumatic Stress Disorder and doubles as an active reminder to not stray from his original purpose of vengeance. He blames himself for being weak-willed during that moment, even though he was but a child. He was able to make use of these negative emotions, however, to exemplify his acting performance during his scenes in the Tokyo Blade Theatrical.

Despite this, he does genuinely care about the people close to him. He's unwilling to let his sister become an idol suffer the same fate as their mother. Thus, he surreptitiously destroys every chance her sister may get to be promoted due to this overprotective nature, despite knowing how she'd long to be famous. He helped the new B-Komachi group in preparing for a gig so they could accomplish a task long thought impossible. He was also one of the main driving forces behind a project that served to save Akane Kurokawa's reputation.

After being told that his father, the main reason for his quest for vengeance was dead, he becomes more warm to those around him and began smiling more. He ponders whether he could now be happy and live normally as he recalls his girlfriend's smiling face. Moreover, he becomes more supportive of Ruby's ambitions and encouraged her to do her best. He was deeply ashamed of himself for continuously using Akane for his own selfish ambitions, but after she broke down, he wiped her tears and vows to keep her safe as he gave her their second kiss that was removed from ulterior motives.

Etymology

 * The name Aquamarine means "love, affection" (愛) (a), "long time" (久) (ku), "love, affection" (愛) (a) and "sea, ocean" (海) (marin).
 * His nickname Aqua means "water, sea-blue, one from water" in Latin.
 * The name is also associated with a blue-green color, which reflects on his eye color.
 * Aquamarine's surname Hoshino means "star" (星) (hoshi) and "field, wilderness" (野) (no).

Trivia

 * Everyone calls him "Aqua" because "Aquamarine" is too long.
 * Ai Hoshino (Aqua's mother) had one star in each eye where Aqua inherited a star in his right eye while his sister Ruby Hoshino inherited it in her left eye. After the revelation that his "father" was 'dead', he lost the star, implying it’s a feature that is dependent upon their emotional state.
 * Aqua reveals that he can't really use technology like the youngsters do nor does he understand the reason behind their popularity.
 * Aqua is constantly called and labelled a sis-con (a person with an unusually strong attachment to their sister).
 * Aqua spent over five million yen when trying to find out who his biological father is.
 * Aqua dislikes bell peppers.