I'm Not the Protagonist's Golden Finger

Su Qingshi transmigrated. (Secret identities + System + transmigration + no CP)

She transmigrated to a steam age where different races lived together under the unified rule of the Federation. She didn't become a noble with every comfort, or even a commoner. She became a thief, one whose every last bit of value had been squeezed out, who had been abandoned in the slums with a raging fever and barely clinging to life. Just as she was desperate, a pair of hands rescued her...

Years later, in the dead of night, a group chased a sickly young man into an alley. The gears of fate began to turn...

"System, you say he's the protagonist? Did I transmigrate into a book? Then what am I? The villain? A cannon fodder character? The female lead?"