Tsumugu Otome to Taishou no Tsuki

The high school girl Tsumugu was knocked unconscious during an earthquake, and when she woke up she found herself in Ginza in the year of Taisho 10 (1921). Lost and confused, she was rescued by Itsuki, a duke's daughter, and started attending a girls' school with her. What will happen to the future of a girl who has drifted to the distant past...?
(Source: Seiga Nicovideo, translated)
Note: Chapter count includes three bonus chapters.