everytime a manga sets the time traveller premise so close to the world wars it makes me feel bad about the characters lol
The 1923 Great Kantō earthquake is a closer issue for these characters considering that they live in 1921 Tokyo, just a couple years away from it.
Tho it's probably not worth worrying about as I doubt a manga like this would want to inlude almost half of Tokyo beoming homeless and many people dying (including a massacre of about 6000 Koreans in the aftermath, something still denied by the Japanaese far-right)
If anything, the author could probably use this event as what brings her back to her time, so the aftermath in 1923 wouldn’t have to be shown.
Not sure what would be more tragic. Itsuki & the rest dying in the earthquake, ensuring nothing she does changes the future. Or returning to her time to meet a 112 year-old Itsuki on her deathbed.