 Alright, so this is one of the stock manga/anime misunderstandings. It puts tension between the male and female characters and allows for a bit of fanservice.
 In my defense, Kimberly's reaction isn't so much an "Eek! He saw me naked and must be some kind of pervert". It's a subtly combination of "What the hell were you doing there?", "That was a surprise", and, of course, "You owe me a new shower curtain".

 I'm going to say that she put up the "closed for lunch" sign when they left the previous night.
 When in doubt, make things more complicated.
Something Else pt 7
drawn by Isabel Marks
|
|