Shift! The Side-Character Heroine

An introverted girl has had enough of the isolation inadvertently formed by her self-imposed isolation. Things changed when she discovers that she has the ability to transverse across the fabric of our universe into the dimensions of multiple storylines. Not only do these storylines leave her with invaluable lessons – they also impart a portion of their power – if she is deserving of it. The time has come for Zhao Youyue to change her fate. She will be a Side-Character, or perhaps…something more! — Description from novelcodex.org