To complete the "Sugar in Danger" Quest, you need enter the Quest field filled with monsters.
If your character dies while fighting the monsters, your character will respawn in the previous field and you won't be able to re-enter the Quest field.
In order to proceed with the Quest, you need to open the Quest UI, forfeit the "Sugar in Danger" Quest, and accept it again.
Please take extra care to keep your character alive from the monsters!