Lagoon Engine(2002)

Lagoon Engine

Yen and Jin are brothers in elementary school and successors in the Ragun family craft of defeating evil spirits. In this world, the battle with spirits comes down to a game of guessing your opponent's "name." Once you know the name you gain control over the fight. Both Yen and Jin have secret names only they know ... and must keep them secret or risk death!

(Source: Tokyopop)