Transmigrated into a Book as a Background Character, I Came Clean to the Demoness from the Start

What should you do if, after you transmigrate into a book, you're neither the protagonist nor the villain, but just an ordinary demonic-sect disciple who lives for half a chapter, has no lines, and is written out like a nobody? I'm desperate for an answer...

The protagonist was already taking off and would soon turn Jiang Linfeng into experience points. Luckily, his System awakened: change the plot and grow stronger. Jiang Linfeng had no choice but to find the villainous female demon and reveal that he was a transmigrator...

"Excellent. Starting today, you are the Holy Son of my demonic sect!"

Ding! The female demon has been detected killing the protagonist. The plot has been successfully changed. Reward: God-Tier Divine Elephant Suppressing Prison Strength!

Ding! The Daughter of Destiny has been detected falling for the Host. The plot has been successfully changed. Reward: God-Tier Great Wilderness Heaven-Prisoning Finger!

Ding! The Destined Villain has been detected having a complete mental breakdown and giving up entirely. The plot has been successfully changed. Reward: God-Tier Ancient Desolate Saint Body!

This novel and its characters are entirely fictional. Any resemblance to real people or events is purely coincidental. Do not imitate.