A Delinquent Past
When Tsubame was still in high school, she was known to be a bit of a delinquent and a troublemaker. She often preferred to do things on her own, not caring much about what other people thought. This resulted in her going through life without many close friends.
Tsubame herself was fine with this; however, looking back when she had graduated, she wished that she would've been friendlier and cheerful, and not as reckless as she had been before.
At some point in time, Tsubame met Shuuichi, her future husband-to-be, who was seven years older than her and also worked as a local politician in N-City. The two of them had gotten married and conceived a child. It was at this point that Tsubame began to stay more indoors, as she didn't want any possible rumors of her pregnancy to spread. Shuuichi worried for her well-being, but Tsubame insisted that she would be fine.
In order to keep herself busy in solitude, she played a social game known as Magical Girl Raising Project, a free to play game that allowed her some sense of distractions as she spent the days in her house.
This led to the Mascot of the game, Fav, approaching her and transforming her into a real Magical Girl. At first, Tsubame refused, especially due to her pregnancy. However, Fav assured her that as a Magical Girl, she would have a safe pregnancy, as her Magical Girl form would both hide her pregnancy and protect her baby. Hearing this, she accepted and was transformed into Top Speed.
Later on, Top Speed would note that the next Magical Girl to be selected would be trained by Calamity Mary, a known dangerous Magical Girl. Top Speed knew about Mary's violent nature and didn't want the next Magical Girl to suffer at her hands, the same way Mary's last apprentice did.
With that in mind, she requested Fav to aid her, asking to take on the apprentice in lieu of Mary. Fav agreed, and the next Magical Girl, Ripple, was given to Top Speed instead of Mary.
Their first meeting was one-sided, with Top Speed being more happy-go-lucky and friendly, and Ripple being less than pleased with how Top Speed acted. For most of her apprenticeship, Ripple found Top Speed annoying, though Top Speed herself would always try to help Ripple whenever she could.
At some point after their first meeting, Calamity Mary visited the two, angered that Top Speed took her next apprentice away from her. Top Speed, wanting to diffuse the situation, played a submissive role and apologized to Mary. However, Ripple, who was more aggressive, showed no fear to Mary, whom the latter disliked. After a brief scuffle, the rivalry between Ripple and Mary had begun, and it would only increase from there on out.
The Eliminations Begin
Fav then announced that the number of Magical Girls in N-City had reached a peak and that he was reducing it down from 16 Magical Girls to 8 using an elimination method based on Magical Candies. This revelation shocked many Magical Girls, who were confused as to why they were being cut in half in the first place. Fav, however, was adamant about it.
Top Speed focused hard on gaining magical candies, despite her apprentice's reluctance to do so. She performed nightly patrols around the city and always kept watch for any trouble around the highways, which she could take care using her broomstick, Rapid Swallow.
Despite not having the advantageous powers that Magical Girls like Snow White possess, Rapid Swallow allowed Top Speed and Ripple to zoom past the city in order to see anyone in need of help.
During the first week, it was announced that Nemurin had been eliminated for having the least amount of candies out of all of them. The Magical Girls bade their farewells to her and continued with their competition. However, it was later discovered that Nemurin had in fact died, and that elimination from the competition meant death in real life. Top Speed was devastated by this, particularly because Nemurin, along with other Magical Girl veterans, were her close friends. Despite the situation, Top Speed continued to patrol with Ripple.
After the second eliminations were announced, Sister Nana contacted Top Speed in order to propose a team-up. Top Speed agreed, despite Ripple's distrust, and they met up with each other. Sister Nana and her partner Weiss Winterprison were looking to create an alliance of Magical Girls in order to get through the eliminations and find a way to stop them. Top Speed agreed with the proposal and vowed to keep herself and Ripple out of any sort of trouble.
During this period, Top Speed and Ripple doubled their efforts, and Ripple began to harness her magical powers a lot better. As the two of them took a short break, Top Speed began to share bits about herself to Ripple in an attempt to become closer with her apprentice.
She learned that Ripple had little to no social life at school and lived alone at her apartment. Top Speed herself shared that the reason she looked out for Ripple is that Ripple reminded Top Speed of herself when she was younger. Top Speed mentioned that despite what may happen, she would try to continue living for another 6 months. Although it wasn't clearly stated when asked, Top Speed had wanted to live this long to see her baby being born.
It was during this time that Ripple was contacted by Calamity Mary, who demanded that she meet with her to battle. Despite Top Speed's insistence, Mary threatened to kill innocents if Ripple didn't show up. Faced with this choice, Top Speed reluctantly agreed to help Ripple fight Mary.
Top Speed and Ripple found Mary holed up above a hotel near the National Highway, where she had already begun to terrorize the people using the highway. As Ripple fought Mary, Top Speed provided as much support as she can. All the while, other Magical Girls such as Snow White were busy helping those injured in the attacks.
As Mary rained bullets from various weapons towards Rapid Swallow, Top Speed and Ripple began to run out of options. Zipping through the skies, Mary had destroyed almost all the surrounding buildings, as well as the hotel she had holed up in.
Finally, Ripple had a plan. By throwing a large glass panel, she managed to trick Mary into shooting it to pieces, using her powers to ensure the glass shards violently stabbed Mary to death, killing her in the process. With Rapid Swallow riddled with bullets, and Ripple and Top Speed exhausted after a long battle, the two took a break, and for the first time, Ripple felt a huge bond form between herself and Top Speed.
Unfortunately, that was cut short when Swim Swim appeared and stabbed Top Speed from behind using her halberd. Though Ripple tried to get her to safety and fought off Swim Swim, the wound was fatal, and Top Speed succumbed to her wounds.
Upon Top Speed's death, her unborn child died with her.
Blaming herself for Top Speed's death, Ripple took it upon herself to kill Swim Swim to avenge her friend. She would successfully accomplish this, but at the cost of her left arm and eye. Afterwards, seeing that Top Speed was right and she was too reckless, Ripple decided to try to calm down a bit. She also became very protective of her next partner, Snow White, not wanting to lose her as well. Years later, Ripple tried to continue to the extent her boundaries, believing it was what Top Speed would have wanted.