Gorou Amamiya/Plot

Introduction Arc
Gorou worked his residency years in a hospital located in the town of Takachiho of Miyazaki Prefecture, where he met Sarina Tendouji, a child patient affected with anaplastic astrocytoma. During this time, he was introduced to her oshi, Ai Hoshino. They discussed reincarnation, and Gorou motivated Sarina to become an idol after she recovered, even promising to consider marrying her when she was 16, but she died at the age of 12. Perhaps seeing Sarina in Ai, Gorou became a devoted fan of the idol, wanting to watch over Ai's path, which Sarina wanted to walk.

Four years later, Gorou became a doctor in the gynecology department at the same hospital. He was caught by a nurse watching B-Komachi's performance in a patient's room, and she informed him about the news of Ai's hiatus. Explaining his reasons, Gorou told the story about Sarina to the nurse, which the nurse chalked up to being a sob story to justify his own obsession with Ai.

Afterward, Gorou met with another patient, a 20-week pregnant teenage girl accompanied by her guardian. It was then revealed that the girl is Ai, and her guardian is her company president, Ichigo Saitou. Shocked by the pregnancy, Gorou battled over his feelings of being a fan and his moral obligation as a doctor. Gorou would later talk with Ai about her twin children, hearing about her belief that lies are a form of love and her declaration to keep being an idol while having the twins secretly. He assured his idol that he would safely deliver them both, owning up to his position as a fan.

They spent the next few weeks together, working on the process of keeping things secret and options for delivery that would not hinder her career before she decided to do it naturally. The night of the due date, Gorou was approached by someone who knew about Ai's pregnancy and his role in it. He chased him away to a mountain trail but then was murdered.

He then reincarnated into Aqua Hoshino, who was born that night along with his sister Ruby Hoshino.

Later on, a personification of Aqua's guilt over Ai's death manifested as Gorou, who would lambast him over his inability to save her and thoughts of moving on and reliving his new life.

During Aqua's trip to Miyazaki, more of Gorou's past is revealed. His mother died shortly after birthing him on her own due to postpartum hemorrhage, having hidden her pregnancy from her parents. Without knowing who his father was, Gorou was sent to the care of his grandparents. Inspired by novels he read about doctors, Gorou decided to enter medical school to become a surgeon but instead became a gynecologist because his grandmother thought he wanted to be because of how his mother died.

It was also revealed that Gorou was there during Sarina's final moments, with Sarina making him promise to take care of her Ai Hoshino keychain she got in a B-Komachi concert when she was well, to treat it as if it was her. He also heard Sarina's confession of love and how she hoped to be reborn, presumably so in the next life that she could be with him, but she died before finishing her words.