The apartment building that Kumiko lives in is shown in several episodes of Sound! Euphonium. The building and the location is in 2 different places, so I went to visit both.
Image from S1E5 - 12m27s
Here's the actual location. It's near Ajirogi-no-michi Street where the bench that Kumiko often sits on is located.
Image from S1E1 - 16m26s
And here's the building. It's close to Keihan Rokujizō Station. I've marked the path from the location to the building in the map below.
These locations were visited on 2015/11/03 and 2015/11/04.
Special thanks to the ones who went here before: