Prologue

ARC ProloguePrologue (プロローグ) arc is the first arc of Oshi no Ko manga series. Prologue arc span the entire first volume of Oshi no Ko, and tells the story of how Gorou reincarnated into the son of his oshi, Ai Hoshino, and his childhood as Aquamarine Hoshino.

Summary
Gorou Amemiya is a gynecology doctor who are a fan of the famous idol Ai Hoshino, being passed this adoration for idols by her late patient Sarina Tendoji, who was a fan of idols herself. One day, while he's working, he handled a patient who turns out to be Ai herself, accompanied by her guardian and company president Ichigo Saitou, revealed she's expecting twins. Ichigo claims that Ai's career as an Idol would be ruined if word got out about her pregnancy, and when Ai asks for Goro's opinion, he states that the final choice lies with her.

Afterward, on the hospital rooftop, Goro and Ai have a heart-to-heart about their lives, invlving, about Sarina, why Ai is not in Tokyo, and how Ai will keep her twin siblings hidden from the public so she csn continue her career as idol, explaining that lies are the most exquisite form of love. Listening to this resolves Goro to ensure that he safely delivers Ai's children for her, as a doctor, and his fan.

On Ai's expected delivery day, Goro gets murdered by one of Ai's fan, as he tried to stop this misterious man, that somehow knows the idol's locstion. As Goro's consciousness fades, he gets reborn as one of Ai's twins, Aquamarine Hoshino. Aqua's twin sister, Ruby, is also introduced, revealed to be the reincarnation of Sarina. From there, Aqua questions how this the man got to know the hospital location, but decides to make the best of his life while being with Ai.

From there, both Aqua and Ruby discovered both of them are reincarnations with all their past memories and knowledge, but decide to act as normal babies for their sake and Ai's.

One day, as Ai leaves to perform her idol duties again with Ichigo, leaving Miyako, the one in charge of babysitting her twins again. Having a rage attack, she starts taking pictures of Ai's health records, showing that she was pregnant with twins as a way of starting a scandal. Aqua and Ruby confront and trick her so she stops, and after the twins convince Miyako from not doing anything reckless, she becomes the only one who knows about they being able to talk.

Time later the twins are able to attend a mini-concert where they watch their mother's group perform with the company of Miyako. Amid their mother's performance, they unintentionally draw attention to themselves by cheering with the crowd. Their act also went viral with a 2 million viewed video. Ai was also intrigued by it, taking note of a fan's comment about her smile, which Ai claimed she'd use to her advantage.

One year passes, and the twins can walk and talk without secretly needing to do it, though people remark their incredible vocabulary for their age. Also, during that time, Ai accrued new jobs, and her latest one was a minor part in a TV drama series.

One day, director Taishi Gotanda leaves an intense impression on the twins due to his appearance. Aqua would later run into Taishi, who was shocked by Aqua's immense vocabulary, prompting him to invite the little kid to the Ai is participating, by Aqua's request to see her.

On the backstages they meet Kana Arima genius actor, and complains that the twin's mother was an impromptu addition to the film. Later Aqua and Kana play out their roles in the movie, with Aqua having an immense talent for acting. After having their cut, Kana asks Taishi to reshoot the scene, as she proclaims in tears that her acting wasn't up to par with Aqua's.

That afternoon, Taishi and Aqua have a heart-to-heart about Kana's tantrum, communication skills are a big part of acting, and how having a big ego early in life can ruin your future as an actor.

Three years later it's shown that Taishi's film was a hit, but still, Gorou's corpse has yet to be discovered. Enrolled in preschool, Aqua asks Ruby about her identity in her previous life. However, Ruby deflects the question with a lie to avoid being looked down upon because she was young when she died. When their teacher announces it is time for dance class, Ruby runs away in fear and is soon approached by Aqua, who learns that Ruby considers herself a terrible dancer. Ruby then briefly recalls her time as Sarine. having mobility issues. With the help of Ai, Ruby is able to dance, and as she gained more confidence and started practicing her dance routine, Aqua notices she has talent as an actress and a dancer.

On a whim, Ai contacted the twin's father asking if he'd like to see their children. Ai trying to reconnect with their father was brought up after she eavesdropped on a conversation between the twins concerning who their father was. One day, someone visits the Hoshino residence, and the person, holding a bouquet of flowers, stabs Ai in the stomach and then proclaims that he lied to him and her fans. Although wounded, Ai recognizes the manRyosuke, someone who frequently attended her "Handshake" events. Having an attack, Ryosuke leaves the scene broken-hearted as Aqua contacts an ambulance for his mother. As Ai is bleeding to dearh, she embraces Aqua as she laments that her scheduled events will be canceled. Blocked by the doorway leading into the hallway, a desperate Ruby asks happening, and Ai, hearing her daughter's voice, compliments her performance at her preschool event. As a saddened Ai wonders what will her children be as adults, in her very final moments, Ai sincerely tells her children that she loves them, leaving a smile on her face as she realizes she was able to say it, as it was the first time she has said it to them.

And for the first time, it wasn't a lie.

Days after Ai's murder, news of death is announced, and her murderer tried to commit suicide and was pronounced dead at the hospital. Her death drew sympathy from the public. Ruby especially took the public's dark opinions on Ai's death with great disdain, noting how cruel and insensitive it can be.

Time passes by, and Ai's death soon fades from the news, and Ichigo and Miyako adopt the twins. During their mother's funeral, the twins sit in the backseat of a car, and Ruby says that Ai told her she has the talent to become an idol, and Aqua details the dark side to her of that lifestyle. Aqua then realizes that Ryosuke couldn't have killed him in his previous life, nor would he have located Ai's location without an informant. From his deductions, Aqua concludes that the informant is his father and vows to murder him with his own hands.

Approaching Taishi, who was at the funeral, asked that he raise him, leaving him astonished.

Years pass, and the twins are now teenagers saying goodbye to their mother as they get prepare to leave for school. Now, Aqua's revenge begins…

Characters Introduced

 * Gorou
 * Sarina
 * Ai Hoshino
 * Ichigo Saitou
 * Aquamarine Hoshino
 * Ruby Hoshino
 * Miyako Saitou
 * Taishi Gotanda
 * Kana Arima