Reiko Amabuki/History

Episode 5
Through a flashback, she is seen with Saki eating at the Drive-in Tori together with her band.

In the 90's
As the first head of the Dorami motorcycle gang, Reiko led her motorcycle gang alongside her best friend Saki until they conquered the entire Kyushu region. She had a heartfelt conversation with Saki who dreams of having a normal family after retiring from it so that she can live a normal life, which makes Saki wonder what a normal life is.

When Saki was challenged by a gang of rival bikers in a chicken game against a cliff on their bikes, Reiko expressed concern for Saki's safety, but Saki assured her that she would not die. Reiko then looked on in horror and called out Saki's name after her friend jumps off the cliff and dies in an explosion.

Present
Eventually, the gang disbanded and Reiko achieves her dreams of having a normal family by marrying and giving birth to a daughter, however, as her daughter grew older, the two became distant and Reiko expressed shock when Maria became the leader of her old gang of motorcyclists. Reiko realizes that Maria was challenged to do the same challenge that killed her friend years ago and is willing to stop her at any cost, so she takes out her old motorcycle and goes to her daughter's rescue. Reiko might be a stay-at-home mom now, but her brief motorcycle ride shows that she still has some power behind her. However, instead of fighting the rival gang, she begs them to stop, as an actual fight would put her daughter's life in danger.

There she manages to make Misa stop the chicken game. Maria, seeing this, scolds her for being always so delicate and that she is not the same person she was in the past, fortunately, Saki intervenes saving Maria. After Saki repeats the trick that killed her, Reiko punches her in the face and yells at her for being an idiot, as she was there when Saki died and she still has painful memories of when it happened, but thanks to this incident she realizes that her daughter just wanted to impress her and be like her in the past, making Reiko begin to understand her daughter and everything that happened to her. She finally reconciled with her daughter before attending Franchouchou's next concert.

Episode 12
They are seen as extras on stage while Franchouchou sings.

Episode 14
Before meeting Saki it is implied that Reiko felt alone and was beaten by the gangs in the area but she knew how to defend herself very well and it was in those moments, and thanks to the inspiration of White Ryu in Saki, that both became friends. Reiko Amabuki/Sipnosis