Aqua Hoshino/Plot

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

At age 4, Aqua witnesses his mother stabbed by that same stalker after answering the door, who later commits suicide. However, Aquamarine thinks it was 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. During this time, Aqua became the apprentice of director Taishi Gotanda and trained to become an actor. However, because Aqua felt inadequate in his abilities, he decided to work behind the scenes in the entertainment industry instead. However, he still desired to become an actor because of Ai's wishes for him to do so.

Entertainment World Arc
Not long after, Aqua and Ruby applied to Yoto Highschool, a school that offers a Performing Arts Program, which Ruby applies for while Aqua takes the General Education program. Coincidentally, Kana Arima, an acquaintance of the two siblings, is also revealed to be attending the school. Aqua reveals his intentions of joining the school were out of worry for his sister, who then labels him a sis-con after the fact.

After Kana attempted to catch up with Aqua, he allowed her to meet with Taishi, 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, Masaya Kaburagi. 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, suspecting Kaburagi to be a potential candidate as his father. The drama was generally received terribly due to the 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.

Dating Reality Arc
In the show, LoveNow, Aqua perfectly played his character and followed the show's flow with his other colleagues. 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.) He also saved Akane from attempting suicide in the nick of time. He was disgusted at how toxic the fans were and how the adults exploited her for their own profit. On his part, he went out of his way to threaten those very adults and pulled multiple all-nighters to make the perfect video to change the fans' minds.

After introspecting her situation, she decides to have a new outlook that is not too dissimilar to Ai for her and the show's sake. This surprises Aqua and makes him blush when he first sees how similar the two are. However, after conversing with Kana, he realizes that he is still trapped by his feelings for Ai, not the current Akane. Aqua reflects upon his relationship with Ai as his mother and realizes how much he never really knew her. When conversing with Akane and discovering how in tune she was with Ai's character, he started seeing her as someone indispensable for his goal. He went above and beyond for the show's last episode as they had their first kiss live, much to Akane's joy.

Upon the show's end, Kaburagi congratulates Aqua for the positive reviews garnered in 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 confirmed that, for now, it was the latter). Though to appease their fanbase, subsequently, they went on many dates together. Later after the cast's get-together, Aqua talks with Mem-Cho, who reveals that she always aspired to be an idol, but didn't due to her circumstances. Aqua then suggests she join the revived B-Komachi that was in the works.

The First Concert Arc
After establishing the new B-Komachi, Aqua meets with Kaburagi to discuss Ai's history. During their discussion, the Lalalie Theatrical Company came into the conversation - the place Akane works and where Ai first fell in love. Kaburagi stated that he could get in touch with their head, mainly to profit from it. Later on, Aqua involved himself with the new B-Komachi, helping them prepare for their new gig at the Japan Idol Festival by disguising himself as Pieyon, an internet personality who had previously helped the girls.

2.5D Stage Play Arc
Kaburagi, after being told about the stage play of the popular manga, Tokyo Blade, suggested Aqua and Kana join its cast. The representative of the company behind the play, Sumiaki Raida, agreed, seeing it as him doing a favor. All went swimmingly until the mangaka behind Tokyo Blade, Abiko Samejima, visited the practice for the play, along with Yoriko Kichijouji (the mangaka behind Sweet Today.) Abiko stated that what she saw butchered the image of her manga and demanded a whole rewrite of the play. Later, Aqua and his fellow actors visit Yoriko and talk to her about the manga industry, leading them to convince her to talk to Abiko.

After the script was rewritten and the misunderstandings were cleared up, things went by as usual until Kana indirectly reminded Aqua about his past when she advised him to recall something that makes him sad if he wanted to be realistic. This causes him to have a panic attack and collapse on the floor. As his girlfriend, the director tells Akane to take care of Aqua. Once alone, Aqua tells her not to inform his family of the incident as he doesn't want them to worry instead and instead gets her to call somebody else: Taishi. Taishi converses with Akane about Aqua at his apartment, entrusting her tidbits of his past due to her girlfriend's status. Akane was then capable of piecing the puzzles together perfectly.

Unbeknownst to Akane, her theory that Ai had a secret child was correct, concluding that Aqua was her son. When Aqua woke up, he saw Akane crying at his bedside. When asked why, she immediately hugged him and empathized with him that it would be terrifying if her thoughts were confirmed as he'd had no one to confide in, which would be incredibly tragic. Aqua remained speechless as she reassured him that no matter what happened, she'll always be by his side and share his pain if something hurt him. The awe-stuck Aqua asks what she is talking about, and she replies that it was a scary thought she had.

At Taishi's home, Akane made a feast for him, surprising the others with her excellent cooking abilities. Initially, Aqua tried to pretend he had no appetite, which caused Akane to spoonfeed him. Slightly embarrassed, he began eating while commenting that it was delicious in his mind. Afterward, Akane asked if she could see the films when Aqua was younger. Taishi was surprised when Aqua gave his permission despite previously adamantly hiding it, though he told them to watch it without him. At night, Akane went to visit Aqua on the balcony. She then asked why he was in theatre for fame, fortune, or something else. Aqua attempts to dodge the questions though Akane remains steadfast in her pursuit. Finally relenting, Aqua reveals that he is in it to kill someone, but he needs power because that person is high up. He then redirects his gaze to her and inquires what she will do about it.

Without hesitation, she answered that she'd help kill them, which caught him off-guard and told her not to say it so casually. She reaffirms her statement that someone like him would have a good reason for doing something so drastic, and it is not a matter of right or wrong for her. Instead, she is willing to accept the guilt along with him as that is how committed she is to their relationship. Though she would also like for him to do his part as her boyfriend, which was to help defeat Kana and Himekawa, as she stood no chance alone and would probably die from being too upset at losing. This causes Aqua to reflect deeply as he promises her he'll do his part as "boyfriends are responsible for keeping their girlfriends from dying."

They then consulted Taishi for advice and, if possible, did it without emotional acting. After reviewing the script, the only conclusion was simple with Aqua having no choice but to act emotionally. Taishi smiled as he said he'd drill it into him from scratch starting tomorrow.