Sengoku Komachi Kuroutan

One fateful day, a girl time slipped into the Sengoku Era. It was an abrupt enough event to be dubbed god's whim, done to sate hellish boredom. The girl has no power to change the world. She was a very ordinary, common, and plain girl that can be found anywhere. And that girl can do no more than a single thing. Survive the Sengoku Era --- that's all.

Official JP: Comic Earth Star ,Official channel of Comic Earth Star in Nico Nico Seiga

Original webnovel: Shousetsuka ni Narou