Johann was the Corvus silver saint of the Century XX. He is loyal to Athena, but thinks she is Aria, and Mars is a Athena new ally, so, obey his orders.
Johann was sent to rescue Aria from Kouga and the other saints. He was the first silver saint, with Miguel, to fight against the protagonists.
He goes with Sonia and Miguel to fight against Yuna (Miguel tracks herself), but Sonia asks to they don't disturb her own fighter against the bronze saint. But, when Sonia is called to go back to the Babel Tower, Miguel and Johann gets the fight. so, they protect Sonia from Souma (that arrived there).
Johann attacks with his aerokinesis, and almost defeats Yuna and Souma... but Kouga arrives and with his light, blinds Johann momentarily and Yuna attacks his blind spot, and explain how she discovers it (she uses the wind element too, so, Johann can't cheats she). Johann falls and is defeated.
After the war ends, Johann goes to fight against Pallas, as a hero that know who is the true Athena.