He is the one who summons all the devils, mostly because of Carerra. He had originally obtained the ancient book in order to gain revenge against those who had ridiculed him. However, upon seeing Carerra, all reason left him and he seduced her. Unfortunately, he was unprepared for her libido, and was exhausted when she finished (too exhausted for her to take his soul). After Carerra returned to Hell, Ogawa began to miss her after some time, and attempted to summon her once more. However, this was during her five-day confinement, so he summoned Mercedes instead.