Phantasm Project: Theories and Speculation thread

There are many mysteries and unexplained details in the world of Phantasm Project. What are the 7 keys of bravery for? Why does everything have the logo "HEL" written on it? What is the cause behind The Returned? Who were the people who created the ARUFEL? 
This thread is for discussing topics such as these and theorising about the hidden lore behind the mysterious world of Phantasm!
Enjoy!