Unlock the true ending
     After  you  completed  every  quest,  the  last  quest  "Truth in
Darkness"  will  be  reveal  on the board at the Guild. After complete
"Truth  in  Darkness"  quest,  then create the Shadow Gem by using the
item  synthesis  on  Ruby  Prism (from another item synthesis on Aroma
Material,  Brilliant  Stone,  Dunkelhite and Dragon Tongue) and Broken
Gem  (which  you  got from the "Truth in Darkness" quest. And last, go
face the final boss Uroboros and beat him to see the True Ending.