Aqua Hoshino

"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."

Aquamarine Hoshino (星野・アクアマリン, Hoshino Akuamarin) is the titular main protagonist of the series. He was known as Gorou in his past life, a medical doctor who treated patients. He developed an obsession for idols (specifically for Ai Hoshino, an idol of the defunct idol group, B-Komachi) after encountering Sarina, one of his patients who held that same infatuation. He was reincarnated along with his twin-sister Ruby Hoshino, formerly known as Sarina, and is now the child of Ai Hoshino.

In his new life, after the death of his mother, he swore he'd do anything to find whoever was behind it; unrelenting in his goal, unlike his sister. Many of his actions are driven by this very ambition. He is willing to do anything to get closer to the truth.

Appearance
Aqua is a blonde and is quite 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; symboling that he and is sister are one half of their mother.

Due to him being Ai Hoshino's son, people point out their similarities, much to Aqua's dismay; wanting to keep things secretive about their relationship.

Personality
Before the death of Ai Hoshino, Aqua was relatively normal, however, him having the experiences of his past life, he was able to do things unexpected of his age. Performing acting jobs was something he was open to and excelled at.

After his mother's death, however, he was a changed man. He became cold, calculated, cunning, and discreet. He transformed into a man willing to do anything to see his goals through.

Despite this, he does genuinely care about the people around him. He's unwilling to let his sister become an idol because he doesn't want her to end up like their mom. He helped the new B-Komachi group in preparing for a gig so they could accomplish a task long thought impossible. He was even one of the main driving forces behind a project that served to save Akane Kurokawa's reputation.

Story
Gorou was a 30 year old doctor and a huge fan of the idol Ai. He was his fan because of a 12 year old patient of his named Sarina used to adore her, before she eventually died. When Ai was pregnant, she came to Gorou's hospital to give birth to twins. Because he was in charge of her, he was murdered by an anonymous stalker and was reincarnated into Hoshino Aquamarine, the son of Ai.

At the age of 4, Aqua witnesses his mother getting stabbed by that same stalker after answering the door, who later committed suicide. However, Aquamarine thinks it's more than a simple "crazed stalker" situation and believes the stalker had been given information about her location by someone close to Ai, which he theorizes is their unknown father and swears to avenge his mother's death by killing him. Even in the future, this single event traumatized and transformed him into who he is today, so much so that he is seen preventing his sister from becoming an idol, afraid that the same events may reoccur. Although he did get a change of heart after Miyako Saitou, his parental figure, conversed with him about it.

Not long after, Aqua and Ruby applied to Yoto Highschool, a school that offers The Performing Arts Program, the program Ruby enlisted in. Coincidentally, Kana Arima, an acquaintance of the two siblings, was also a part of the school. Aqua reveals his intentions of joining the school was being worried about his sister, Ruby then labeling him a sis-con after the fact.

After Kana made attempts to catch up with Aqua, he allowed her to meet with Taishi Gotanda, allowing them to talk in a more private area. Their conversation eventually led to Aqua's interest piquing after Kana mentioned an affiliate of Ai Hoshino, Kaburagi Masaya. Since he was involved with a project Kana was in, the live-action Sweet Today drama, Aqua uses this as an opportunity to gain more intel about her murder, Aqua suspecting Kaburagi being a potential candidate as his father. The drama was generally received terribly due to incompetent actors and a butchered storyline. Kaburagi's attention was raised when Aqua and Kana acted out a genuinely good scene in the series finale. This provided leeway for Aqua to talk business with him, Kaburagi stating he'd provide info about Ai's background if Aqua acted in a reality dating show.

In the show, he played a character, went with the flow of the show, and his other colleagues, much to his dismay. Later on, he was one of the key coordinators behind a project to save Akane Kurokawa's reputation in the public's eyes (due to a moment involving her and Yuki Sumi.) After introspecting her situation, she decides to play a character not too dissimilar to Ai Hoshino for her and the show's sake. This surprises Aqua, making him blush, but upon conversing with Kana, it was just his feelings for Ai, not Akane. Aqua reflects upon his relationship with his mother, showing him how much he never really knew her.

Upon the show's end, Kaburagi congratulates Aqua for the positive reviews LoveNow, the reality dating show, received due to his presence. Kaburagi then stated he'd fulfill his end of their bargain in the coming week. After their conversation, Akane approached Aqua regarding their relationship (whether it was the real deal or for business. Aqua confirming the latter.) Later after the casts get together, Aqua chatted with Mem-Cho. She reveals that she always aspired to be an idol, but didn't due to her circumstances. Aqua then suggested she join the revived B-Komachi that was in the works.

After the new B-Komachi was established, Aqua then headed to discuss with Kaburagi Masaya, about Ai. During their discussion, "The Lalalie Theatrical Company" came into the conversation - the place Akane Kurokawa worked in and where Ai first fell in love. Kaburagi stated that he could get in touch with their head, mainly profit off of it. Later on, Aqua involved himself with the newly established group, helping them to prepare for their new gig by disguising as Pieyon, an internet personality.

Kaburagi Masaya, after being told about the stage play of the manga, Tokyo Blade, suggested that Aqua and Kana join the stage play. The representative of the company behind the play, Raida Sumiaki agreed, seeing it as him doing a favor. All went swimmingly until the mangaka behind Tokyo Blade, Samejima Abiko, visited the practice for the play, along with Kichijouji Yoriko (the mangaka behind Sweet Today.) Abiko stated that what she saw butchered the image of her manga and wanted a whole rewrite of the play. Later on, Aqua, along with his fellow actors, visited Yoriko and talked to her about the industry, leading them to convince her to talk to Abiko.

After the script was rewritten after clearing up the misunderstanding, things went by as usual until Kana indirectly reminded Aqua about his past. This caused him a panic attack and was given a break. Akane approached Aqua about his worries, and after resting, Taishi arrived at the scene conversing with Akane about his past. He reveals tidbits of his past and after piecing things together, Akane came up with a theory that Aqua was Ai's son. She later comforts Aqua after he woke up from his rest.

Trivia

 * Everyone calls him "Aqua" because "Aquamarine" is too long.
 * His mother has one star in each eye, he inherited a star in his right eye and his sister inherited in her left eye.
 * He says he can't really use technology like the youngsters do.
 * He is constantly called a siscon.