The Day I Entered My Own Setting

Being transmigrated into a cannon-fodder character is scary. But being transmigrated into a cannon-fodder character of your own design, fated to be completely rewritten... that's awesome. First world: He Hongyao, an adopted daughter of the Mu Prince's residence who disguises herself as a boy and poses as a young princess, paired with the rewritten version of the young, aloof sword immortal Mu Renqing. Second world: Jiang Yuyan, the demonic sect's enchantress from The Twin Heroes, paired with a Commander of the Embroidered Uniform Guard. See chapter one for more pairings.