Lagoon Engine 

Yen and Jin are brothers in elementary school - and successors in the Ragun family craft of defeating ghosts and evil spirits! In this world, the battle with these wicked "Maga" comes down to a game of guessing your opponent's true name. Once you know the name you gain control over the fight. While Yen and Jin train to join the family business, the two boys must keep their identities a secret...or risk death!