Transported into Ninjago as the Shadow Master

[Reincarnated before birth; pairing undecided; characters will be anthropomorphized for convenience]

There was once a student who absolutely loved watching Ninjago.

One day, she transmigrated as Lin Walker, the younger sister of Jay, Master of Lightning, and a character who was never supposed to exist.

Burdened by a curse, she was forced to leave the land of Ninjago and seek out her own opportunities.

At last, one day, she returned to her homeland and became the Master of Shadow.

But just when she thought she could use everything she knew to help the ninjas, she discovered that, as someone who should never have existed, every attempt to change fate would cost her time.

[Covering my bases: sorry for the out-of-character moments. The author writes purely out of love, mostly for herself, so please forgive the rough writing!]