Kogasa : Uramesiya~ (A rice-restaurant exists in backyard)
Sanae : Hi,Hi omote ha sobaya. (And, a soba shop faces to the street)

wat

Delta_Wave said:
Kogasa : Uramesiya~ (A rice-restaurant exists in backyard)
Sanae : Hi,Hi omote ha sobaya. (And, a soba shop faces to the street)

I don't get it.

Probably competing shops?

"Urameshiya-" is something ghosts would say. Maybe Kogasa wanted to surprise someone by using it.
The trick is, that it could be written as 裏飯屋 (as in the translation by Delta Wave).

To clarify: in UFO Sanae B scenario, Kogasa tries to surprise Sanae with the now-familiar うらめしや ("urameshiya"), which is meant to be 恨めしや ("I have a grudge"), a typical Japanese ghost thing, but Sanae willfully misinterprets it as 裏飯屋 ("a rice shop in the back") and replies with はいはい 表は蕎麦屋 ("Yes, yes, and out front is a soba shop").

And now that I've written that out once and for all, I'm going to link this post anywhere else that joke shows up on Danbooru, because d'awww, happy Kogasa.