Chapter 121

Sarina Tendouji (天童寺さりな) is the one-hundred twenty-first chapter of Oshi no Ko manga series. It is written by Aka Akasaka and illustrated by Mengo Yokoyari.

Summary
Following Kana's advice about "understanding yourself", Ruby arrives in front of Sarina Tendouji's family home. It is revealed that Ruby comes there whenever she is having a difficult time but was never able to ring the bell. Just as she turns to leave, however, Marina Tendouji opens the door.

Elsewhere, the Tsukuyomi tells her crows Sarina's life story: ''Marina actually greatly loved her, so much so that she fell into a depression upon learning about Sarina's terminal illness. To help his wife, Sarina's father opted to separate them by sending his daughter an isolated hospital. To cope with their daughter's inevitable passing, the parents thrusted themselves into their work, minimizing contact with said daughter while her condition only worsened. In the end, Sarina passed away without ever seeing her parents again. Afterward, upon learning of her daughter's fate, Marina regretted her actions. Over time, however, she had two new children and moved on with her life; THE END.''

Back with Ruby, she is stunned as she watches Marina happily interact with her new children, not even noticing her. Returning home, she finally breaks down as she concludes that her mother never loved her, which is why she wanted Ai as a substitute. Believing she brings misfortune to everyone who interacts with her, be it Marina, Ai, or Gorou Amamiya, Ruby rants to herself why she was reincarnated as Aqua overhears her.

Characters

 * Ruby Hoshino
 * Marina Tendouji
 * Tsukuyomi
 * Sarina Tendouji (flashback)
 * Ai Hoshino (flashback)
 * Gorou Amamiya (flashback)
 * Aqua Hoshino