Motor Girl and the Endless Race. Motor Girl, #1

The day that Rene disappeared was the day Josaline woke up. To get away from her Purist parents, she moves to the city. Josaline misses Rene, but people from mixed tiers -or Alloyed- go missing all the time. It's not until Rene's brother, Glin, starts risking his life to find her that Josaline realizes there's another choice. Glin and Josaline are going to find her, even if it means breaking every law to do so. Of course, Glin doesn't want Josaline's help.
He sees her as his little cousin to protect. He doesn't have a choice since Josaline the better racer, and the facts of Rene's disappearance lead them to an underground racing ring. Things start to look up when the leader of the Cruor, Yuuto, takes an interest in Josaline. But so does the leader of the Kurio-chi, Sora, a group of Mutes that did far worse things than race illegally on rail-broken cycs. Glin continues to try to push Josaline out while Yuuto pulls her in.
It's against the law for Muted Yuuto and a Gilde like Josaline to be together. Telling herself that doesn't change how much Josaline wants to stay by his side. She finds out too late the cost of her selfishness, and Glin and Yuuto will have to pay the price.