yep, your level never goes away, you can play through half the game get to level 20, die. The game will give you an option to reload from last time you saved or restart the game with your current status. Similar to Breath of Fire Dragon Quarter if youve played that. At the start of your new game you will be at lvl 20 with all the abilities/stats youve aquired
So yeah the game is designed to be replayed over and over