Considering the First-Episode Twist of the series involves two murders, Oshi no Ko will make you leak a lot of tears. If Kaguya-Sama is a comedy, then Oshi no Ko is a tragedy.
- Goro's reasons for becoming a fan of Ai: his patient Sarina idolized Ai and introduced him to her videos before dying to cancer. While Played for Laughs with his assistant accusing him of ogling Ai, Goro still remembers and mourns Sarina four years after her death, and even after he is reincarnated into Aqua.
- As revealed later, Goro effectively became a Parental Substitute for Sarina due to her parents never being around her life, even in her final moments. Up until his death, Goro kept a keychain that Sarina gave him, of Ai.
- On Sarina's end, Goro became her First Love due to his kind and caring nature, and she wished to become an idol so he could become her fan, which she couldn't achieve due to her illness and early death. After reincarnating as Ruby, she opts to become an idol and locate Goro once she's famous, unaware that he died shortly before her rebirth and is now her twin Aqua. She eventually finds out about the first part, and takes it very poorly, only finding out the second part right when she needed something like it.
- Goro's death. By all accounts, he was Nice Guy doctor who cared deeply for his patients, and especially Sarina whose death still haunts him even years later. His life and career are abruptly cut short because of a Loony Fan upset over Ai's pregnancy. Worse, he dies with no one but said fan by his side, and his corpse was left to rot for over sixteen years, only to be eventually found by his twin sister and reincarnated patient, who doesn't take it well.
- Despite her growing popularity, Ai Hoshino struggled to understand and express the idea of love for much of her life, and desperately wanted to feel it. With no family or close friends, she remained convinced she could only lie about love during her work as an idol.
- Ai's death. It sets the tone of the remainder of the story and leaves a significant psychological impact on her loved ones and fans, especially her twin children who witness her final moments and death.
- It's only in her final moments that Ai realizes that she's truly grown to love her children, praising Ruby for her dancing the other day and smiling at Aqua before succumbing to her wound.
- This moment becomes even worse when you take Ai's life story into account: after spending nearly her entire life desperately trying to find a way to love, she finally manages to make meaningful connections with people in the form of her bond with her children...and she fails to notice the significance of it until she's on the brink of death.
- Ai's death affects not only the twins but also her manager and Parental Substitute Ichigo. Her death causes him to leave his wife and adopted children and start drinking for the next twelve years.
- It's only in her final moments that Ai realizes that she's truly grown to love her children, praising Ruby for her dancing the other day and smiling at Aqua before succumbing to her wound.
- Akane's attempted suicide. After accidentally hurting Yuki's face on-camera, fans of My Love start harassing her online and at school, driving her into a corner and causing her already-present self-loathing to worsen. It eventually becomes so bad that in her despair, she decides to end it all and jump off of a bridge into traffic, only for Aqua to appear and pull her back. Shortly after, she breaks down crying in the police station, admitting to her mother that she couldn't tell her about her backlash because she didn't want to worry her. In fact, the first thing Yuki does after learning about it is cry her eyes out.
- After a number of dates where the two genuinely care for each other, Aqua breaks up with Akane after discovering her intent to kill his father for him. The latter clearly does not take it well.
- Sarina Tendouji's mother's appearance. A seething Aqua recognizes her and he's barely able to hold himself when talking about the topic of family with her, when he sees a picture of her happy family (consisting of two children and her husband but no mementos or photographs of Sarina) he thinks how Sarina's life was hell. In a way, it's that Sarina was lonely and sad with no one but Goro to see her in the hospital while her mother basically had or showed no care for her and moved on and had two healthy children she loves.
- To boot, when we see Ruby trying to practice on the mom part, Kana lectures her on what she should do to gain the effect by telling her to emulate the feeling of a stranger who isn't loved by their mother and Ruby has dead eyes as she notes every mother would actually love their children deeply and it's wrong to think they did not love you. It clearly shows the pain, hurt, and sadness she had in her past life when her parents didn't bother to visit her in the hospital.
- The Movie arc continues to torture the living daylights out of Ruby's soul as she finally meets her past life's mother face-to-face in Chapter 121. Overwhelmed with nothing but grief as she sees Marina interact with her new children, something she never had in her past life as Sarina, Ruby comes to believe herself to bring misfortune to those who interact with her. This chapter ends with Ruby breaking down over why she was reincarnated, while Aqua watches from the background in silence.
- Chapter 122 brings the twins back together after numerous chapters of estrangement, with Aqua openly saying that he's begging Ruby not to go down a path of revenge like him, knowing he can give her the truth she would want to know, and the end sees both of them crying into each other's arms as they finally realize who each other is.
- Chapter 131 finally has Ai's mother show up in person. As it turns out, she only mistreated her daughter because her fiance was starting to fall for her instead of herself. She also revealed that she only abandoned Ai because she was too scared that she would abuse her daughter again, and is openly regretful about how she treated her, still mourning her loss as much as her associates and children even decades after her death.
- Chapter 133 has Kana lash out at Ruby for both her status and keeping her in the shadows before subsquently spending a few chapters coldly ignoring her. With how serious she sounds, it's easy to forget that what appears to be true hatred for Ruby was actually a risky Zero-Approval Gambit to help her understand her mother's feelings better, such that poor Ruby is genuinely hurt. Fortunately, the two are able to resolve the issue by a few chapters in, with Ruby claiming she's different from her mother, and tells Kana to be more honest and talk to her if there're any problems instead of bottle them up.
- In Chapter 134, Ruby comes to the realization that despite how much everyone around her claims that her mother Ai was an unflappable rock who could bear the weight of hate and jealousy from the people around her with a perfect smile, in reality it most likely hurt her to the point of bringing her to tears but she kept up the facade until she was alone.Ruby: So Ai Hoshino is just a weak, lonely girl after all?
