How to allow OpenLDAP user to write data to SSHFS mount point?

Question

I mounted a network drive (Storage Server) to the directory /home/ldap for all OpenLDAP client computers. If a user login one of the computers, their home directory will be set the mount point as: /home/ldap/users/{username}. Users can read and write to their directory freely.

Now I have a tester account in OpenLDAP named tester4 under group users and logged into one of the computers. After login, I run ls -al to check the permissions.

Location: tester4@Computer1:/home/ldap/users/tester4

$ ls -al
drwxr-xr-x 1 tester4 users     4096 Aug 30 20:57 .
drwxr-xr-x 1 root    usrstomgr 4096 Aug 30 18:17 ..
-rw-r--r-- 1 tester4 users      220 Aug 30 17:57 .bash_logout
-rw-r--r-- 1 tester4 users     3771 Aug 30 17:57 .bashrc
drwx------ 1 tester4 users     4096 Aug 30 17:57 .cache
-rw-r--r-- 1 tester4 users      655 Aug 30 17:57 .profile

I tried to create a directory in this directory but not successful. tester4 is the owner of the directory, why tester4 does not have the write permission?

Location: tester4@Computer1:/home/ldap/users/tester4

$ mkdir no
mkdir: cannot create directory ‘no’: Permission denied

Then, I directly use tester4 to login the storage server and create a directory.

Location: tester4@Storage:/home/ldap/users/tester4

$ mkdir no
$ ls -al
drwxr-xr-x 2 tester4 users     4096 Aug 30 23:02 no

What is the problem disallowing tester4 to write to the SSHFS mount point? The following is the commands (without sudo) I used to mount the network drive in Computer1, where casper is the admin user of Computer1.

sshfs -o allow_other -o kernel_cache -o auto_cache -o cache=no -o reconnect -o compression=no -o cache_timeout=6000 -o ServerAliveInterval=15 casper@{Storage IP}:/home/ldap /home/ldap

Update

If I change the owner of . directory to casper, tester4 can write to the directory. If tester4 create a file, the owner of the file is casper. How can I configure SSHFS to allow other users to write to the directory using their identity?