As someone who has actually been to Sendai and think of it as a beautiful place, there's little that makes it "the Katawa Shoujo city" other than the train station backgrounds.
Aoba Castle's hill is too close to the city itself to be the same hill Yamaku is supposed to be on, and the hill backgrounds are from two other locations in Central Japan and Shikoku.
Perhaps it is best to assume this story could take place in just about any provincial city in Japan where life is slow, even for a youth, and there's plenty of time to think about yourself and others

Could be Aomori, Nagano, Kanazawa, Kochi

>>537757118
Human beings can actually sleep in the presence of natural light, provided it's quiet enough, so darkness seems to have hardly any advantage whatsoever