Prologue

Prologue arc is the first arc in the Oshi no Ko 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 is a gynecology doctor who are a fan of the famous idol Ai Hoshino, who were taking a break because of poor health. 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. After taking a moment to calm himself, he examined Ai and it was revealed that she's expecting twins.

Chapters

 * Chapter 1: Mother and Child (母と子)
 * Chapter 2: Brother and Sister (兄と妹)
 * Chapter 3: Babysitter (ベビーシッター)
 * Chapter 4: How to Craft a Smile (笑顔の作り方)
 * Chapter 5: Director and Actress (監督と女優)
 * Chapter 6: Child Actors (子役達)
 * Chapter 7: If You're Scared of Falling, You'll Fall Even More (転ぶの恐れれば余計に転ぶ)
 * Chapter 8: Ai Hoshino Part 1 (星野アイ前編)
 * Chapter 9: Ai Hoshino Part 2 (星野アイ後編)
 * Chapter 10: Introduction (イントロダクション)

Introduced

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