Sorry,Key Jack 4 is not avaiable yet. We will update Key Jack as soon as it is released.
If you want to read new chapter of Key Jack at the first time,you can subscribe it. We’ll send your the email as soon as Key Jack 4 updates.

Have more fun on facebook:

https://www.facebook.com/mangahomelife/

Or enjoy fantasy shoujo moments on tumblr:

https://onlyshoujo.tumblr.com/

You can read some other great manga to kill time