I think it's because they were in the entry way of the apartment. Usually in some Japanese houses/apartments they're lower so I think they're around the same height, but idk I could be wrong
The story is a bit confusing but it's because you have to read it completely in one go or remember the previous chapters in detail so you can understand but it's still very good And don't forget to read the original work to understand the uke past
Guys, it's officially on Webtoon now if you want the official translation and there's 7 chapters available at the moment