Google Storage does not work like a regular file system as in Windows/Linux. It appears to have folders but in the background it behaves as it does not. It only allows us to create "folders" so we can organize better and for our comfort.
If you want to save data in specific folders from gsutil try this.
gsutil cp [filetocopy] gs://your-bucket/folderyouwant/your-file
It will store the item in a "folder".
Check this link for more gsutil cp information.
This is the logic behind Google Cloud Storage "Folders".
gsutil will make a bucket listing request for the named bucket, using
delimiter="/" and prefix="abc". It will then examine the bucket
listing results and determine whether there are objects in the bucket
whose path starts with gs://your-bucket/abc/, to determine whether to
treat the target as an object name or a directory name. In turn this
impacts the name of the object you create: If the above check
indicates there is an "abc" directory you will end up with the object
gs://your-bucket/abc/your-file; otherwise you will end up with the
object gs://your-bucket/abc.
Here you have more interesting information about this if you want.